Popular Science Monthly/Volume 4/January 1874/Concerning Serpents
|←Notes||Popular Science Monthly Volume 4 January 1874 (1874)
By Elias Lewis Jr.
|The Theory of Molecules→|
FEW animals are more universally feared and detested than serpents. Their presence startles us, however inoffensive they may be. Nor can the gracefulness of their motion, or beauty of color, conquer the discontent we feel when we see them gliding in our path, or coiled and glistening in the sunshine, in which they delight. The enjoyment of many a summer's ramble has been impaired from this cause, and we fear our article may be as distasteful to many persons as are the objects of which it treats. But we may remember that serpents, no less than more attractive creatures, are important in Nature's economies. Their structure is a marvel of mechanical adaptation, less complicated, perhaps, but as perfect in every detail as is that of mammals and birds, and the mechanism which rolls the human eye is not more complete, and scarcely more wonderful, than that which moves the fangs of a viper. Perhaps, in the study of Nature, we should estimate objects by their fitness, rather than by their attractiveness or beauty.
"The serpent," observes Prof. Owen, "is too commonly looked down upon as an animal degraded from a higher type. . . . But it can outclimb the monkey, outswim the fish, outleap the jerboa; it has neither hands nor talons, yet it can outwrestle the athlete, and crush the tiger in its embrace." Serpents, in their mode of locomotion, are creeping animals, as their name implies, and constitute an order of the great class Reptiles. This term also implies creeping, but includes orders of animals which have limbs for locomotion, and do not creep. Of these, turtles, lizards, and crocodiles, are familiar instances; so that animals of several species, which run, walk, or swim, are included in the same class with those which creep. All of these, however, are cold-blooded, the temperature of the body differing but few degrees from that of the surrounding air or water. Their coldness is always obvious to the touch, and this is true with those found in hot as well as in temperate climates, and adds greatly to their repulsiveness.
|Port Natal Rock-Snake, or Python.|
Of serpents, their general form and structure are the same. Their bodies are rounded and elongated, and covered with a scaly skin. The vertebral column is continuous with the length of the body, and is divided into joints from 200 to 400 in number, but in the large pythons (Fig. 1), as stated by Dr. Carpenter, 422 vertebral joints have been counted. To about 360, or 6/7 of these, were attached pairs of movable ribs. A rattlesnake, with 194 vertebræ, had 168 pairs of ribs. The vertebrae of the serpent are united by a most perfect ball-and-socket joint, and the ribs are joined to the vertebrae in a similar manner. These, held and worked by complete muscular adjustment, give to several their wonderful flexibility, strength, and crushing power.
The well-known boa-constrictor, and the aboma, or ringed boa of South America (Fig. 2), are illustrations of this class of serpents, the term constrictor being given from their power to close upon and compress whatever is within their folds.
The structure of the backbone of a serpent has direct relation to its locomotion, for it is without limbs, and rudiments of pelvic bones are found only in the boas, pythons, and a few other species. But, where the type shades off into allied reptilian forms, the rudimental limbs are developed and prominent.
We read that the curse pronounced upon the serpent was, "upon thy belly thou shalt go," and the inference seems to be that, previous to that time, its mode of progression was not upon its belly. This would imply a great anatomical change in the structure of the creature at the time in question, a change which, so far as we are aware, is not proved by paleontological research, and the expression is probably a figurative one, as observed by Dr. Buckland. Serpents progress by the "foldings and windings they make on the ground," and the stiff, movable scales which cross the under portion of the body; but the windings are side-ways, not vertical.
The structure of the vertebræ is such, that upward and downward undulations are greatly restricted, and many illustrations, showing sharp vertical curves of the body, are exaggerations. Most persons have seen snakes glide slowly and silently, without any contortion. They seem to progress by some invisible power; but, if permitted to move over the bare hand, an experiment easily tried, a motion of the scales will be perceived. These are elevated and depressed, and act as levers, by which the animal is carried forward. Nor can a serpent progress with facility on the ground, without the resistance afforded by the scales. It is stated that it cannot pass over a plate of glass, or other entirely smooth surface. We saw the experiment tried, by placing a small pane of glass in a box, in which was a common black snake. He was made to pass over it repeatedly, but evidently found that he had no foothold on it; and the third time, as he approached it, elevated the fore-part of his body slightly, and brought his head down beyond the glass, and, on passing, his body seemed scarcely to touch it. This gave an opportunity to witness the wave-like movement of the scales, that is, of their elevation, which runs from the head to the tail, enabling the animal to move continuously, instead of by a series of minute pushes, as would occur if all the scales be lifted and depressed at once.
In the moulting of the snake, which occurs yearly, and sometimes oftener, the outer covering of these creeping scales is shed; this is true also of the covering of the eyes, so that the cast epidermis represents, with great distinctness, the external features of the animal. In moulting, the outer skin is broken along the back, near the head, and the animal emerges, frequently drawing with him the skin, turning it inside out. Prof. Owen states, however, that in one instance exuviation commenced by the snake rubbing the skin loose around its jaws, working it back against the sides of its cage, when, putting its head through coils made by its own body, it pressed back the skin, turning it outward. We have observed that the black snake, on moulting, becomes more sensitive and irritable, but shy, and inclined, for a day or so, to keep close in a corner of his cage. The scaly covering of serpents must diminish their acuteness of touch; but we have found them sensitive to exceedingly slight irritation. They are without an external ear, and the phrase "deaf as an adder" is a familiar one. Nevertheless, they have organs of audition beneath the skin or protecting membrane, and we know by experiment that snakes hear and distinguish sounds, and are said in some instances to recognize the voice of their keeper. Some species, it has been observed, are influenced by music, and we quote the statement by Chateaubriand of an incident witnessed by himself. He says: "The Canadian began to play upon his flute. The snake (a rattlesnake) drew its head backward, its eyes lost their sharpness, the vibrations of its tail relaxed, and, turning its head toward the musician, remained in an attitude of pleased attention."
The snake-charmers (Fig. 3), familiar to travelers in Eastern countries, handle cobras with apparent impunity, cause them to advance or retreat, to coil and uncoil, to bow their heads, or bring their deadly mouths to their own by musical sounds, either vocal or instrumental. A story is related of an English gentleman, residing in a mountainous part of India, who was compelled to desist playing upon a flute because the music attracted serpents to his residence. The sense of taste in serpents must be very feeble, as it is quite unserviceable. They swallow their food whole, nor have they any teeth by which mastication can be accomplished. Their sense of smell is also obtuse. The
organs by which this is effected are near the muzzle, but, according to Cuvier, they are without the sinuses which exist in the heads of mammals. We have tested this sense in several species of snakes, but only pungent odors seem to specially annoy them. The tongue of the serpent is a harmless appendage, tough, horny, and double-pointed; and, like the same member in man, has a wonderful propensity to be in motion. That snakes sting with their tongues is an old but erroneous opinion. Perhaps our own species is not equally innocent in that respect. All serpents are carnivorous, and nearly all seize and swallow living food. Their teeth are bony, hard, conical in shape, and exceedingly sharp-pointed. None of the class have grinding or cutting teeth. They are formed for holding their food, not to grind, crush, or cut it. Moreover, all their teeth are recurved in form and position ; that is, they point in or backward, so that an object once seized can scarcely escape, and, if the jaws be fully distended, could only with great difficulty be ejected. Instances are given where serpents have died from their inability to swallow what they could not eject from their throats, and it is obvious that life could not continue a very long time under such circumstances, for, as Prof. Owen observes, "while swallowing, the tracheæ may be so compressed that no air can pass, and their only resource is what is contained in the lungs."
In the non-venomous species, which includes those that constrict or crush their prey, are found four rows of teeth in the upper jaw and arch of the mouth, and two rows in the under jaw. Venomous species have usually no more than two rows above, which are on the palatal arch, and two below; but they have on the upper jaw two or more poison-fangs, as shown in Fig. 4, an account of which makes the most fearful chapters in the history of this family of reptiles.
|A. Diagrammatic Section or the Eye of a Viper.
a. Eyeball; b. Optic nerve; c. Chamber into which tears are poured; d. Epidermic layer covering the eye.
|B. Head of Viper, showing Poison-Fangs.|
We have observed that serpents swallow their food whole. They make a meal from a mouthful, but the mouthful is sometimes a very large one, for they will swallow animals twice or thrice their own diameter. This is permitted by the extraordinary expansibility of their body; but the enlargement of their jaws is a complicated phenomenon. In the act of swallowing, they yield at every point, side-ways as well as vertically. The elastic integuments which hold the parts of their jaws in place give way, and the apparently small mouth becomes an enormous one.
Digestion proceeds slowly, and, if the meal be excessive, as it often is, the serpent remains sluggish and comparatively helpless a long time. "They have been kept four, six, and eight months, without being fed, and with very little apparent waste of substance." Bruce reports that he kept specimens of the cerastes, or horned-snake, two years in a glass vessel without food, during which time they cast their skins as usual.
Vital activity in serpents is low. In mammals, the normal mean temperature is from 95° to 105° Fahr., and this must be maintained, or disease supervenes. With serpents, the temperature is a few degrees only above that of the surrounding atmosphere, and varies with it. Thus, it may range, in their healthy active state, from 60° to perhaps more than 80° Fahr. The temperature of a serpent was found, by Hunter and others, to be 88.46°, that of the air being 81.5°. The temperature of a frog was 48° in water at 44.4°. If the atmosphere be continuously at 60°, some of our common snakes become sluggish and inactive. In both mammals and reptiles the source of internal heat is the same, the difference being in degree only. The low temperature of serpents (as of other reptiles) arises from the structure of their vital organs, by means of which their blood is imperfectly oxygenized. As the "worn-out" or venous blood enters the heart, it is mixed with the vitalized blood from the lung (there being, in most species, only one lung and a rudiment of another), and it is this mixed blood which is thrown into the general circulation, as shown in Fig. 5. The blood of a serpent has been said for this reason to be
only half alive, and their functions are accordingly sluggish and dull. Their power of existence for long periods without food, and with little waste of tissue, is chiefly incident to their low vitality.
Hibernation is with them a period of profound torpor. In our temperate climates they gather in large numbers, in some hole, or row in the ground, or in clefts of rocks, for their winter sleep. We once saw twenty-six black snakes taken from one burrow beneath the roots of a partially-fallen tree, in February. Other observers have found a much larger number. We are informed that more than 300 have been found in a single burrowing-place, and that many species, venomous and non-venomous, sometimes resort to the same rendezvous and hibernate together. In the tropics the anaconda (Fig. 6), and perhaps other species of serpents, sometimes hibernate during the dry season of summer in the hardened mud of dried-up pools. It is by the power to hibernate that serpents survive during the winters of temperate climates, but they seem unable to withstand the extreme and long-continued cold of the arctic zone. There, serpents, and indeed
reptiles of all kinds, are rare, and frequently are entirely wanting. In the Falkland Islands, Terra del Fuego, and the mountains of Southern Patagonia, no serpents have been found. The persistence of vitality in serpents is extraordinary, and continues after great mutilations. They are said to have lived several days after removal of the head and viscera. One placed in a vacuum twenty-four hours still showed signs of sensibility; and, many hours after decapitation, a rattlesnake would plunge its headless trunk as in the usual act of striking.
In temperate climates serpents as a rule are less fierce than in the tropics. In North America the Crotalidœ comprise twelve species with rattles, and three species in which rattles are absent. Of the last named, the copperhead and moccasin snakes are well known. Of the first, the northern rattlesnake (Fig. 7) is familiar, and unpleasantly abundant in many parts of the country, but is nowhere fierce or inclined to attack. Fig. 8 is of the common viper, or adder of England and the Continent.
All the gigantic crushing species are found in regions of torrid temperature. Of these, the Guinea rock or fetich snake (Fig. 10) is allied to the family of pythons already noticed.
There too are the most terribly fierce of the venomous species, as the fer de lance (Fig. 11); the cobra (Fig. 12), sacred in India, the killing of which with some tribes is considered sacrilege; the haje or spitting-snake of Africa, a hooded species, and allied to the cobra, and the horned puff-adder (Fig. 13), whose poison is used to tip arrows by the South-African Bushmen.
The mere recital of their names excites in one unpleasant sensations. Deaths from the bite of serpents in temperate regions which they infest are surprisingly rare. It is otherwise, however, in the tropics, and perhaps no country has so fearful a mortality from the bites of venomous snakes as India. In six provinces, which include Assam and Orissa, with a population of about 121,000,000, 11,416 deaths were reported in a single year. This is about one in every 10,000 of population, and this is only an approximation to the actual mortality, for many districts sent no returns. A majority of all the deaths from this cause was from cobras; yet this serpent, as served, is an object of veneration, and is regarded with peculiar deference. If found in their houses, as it frequently is, it must be petted, cared for, tenderly fed, and propitiated, for it is an object of worship, and occupies a high place in the mythology of the Hindoos. Indeed, the worship of serpents seems to have been widely adopted, and figures more or less in a vast number of the religions of the world. It is often referred to in the Scriptures, and is a subject of elaborate discussion in the profoundly learned and interesting volume of Ferguson, on "Tree and Serpent Worship."
We mentioned the fact that in most species serpents have but one fully-developed lung. Into the cavity of this the trachea or windpipe terminates, and it has been stated that they "in a manner swallow air." What takes place in the process of breathing appears to be this. Unlike mammals, serpents have no diaphragm, but by a movement of the ribs the cavity of the body is enlarged, and, a pressure being thus removed, the lung inflates and expands by the air passing into it. Another and opposite movement of the ribs expels the air, whence it appears that their process of breathing is essentially the same as in mammals. Nor are their lungs in structure essentially different. The air sacs or cells communicate with the principal pulmonary tube, but a vastly smaller surface is exposed to the inhaled air, and aëration of the blood is consequently extremely imperfect and incomplete.
Serpents are without proper organs of voice, the vibrating membranes being absent. The passage of air into and out of the lungs, if hurried and rapid, produces a hissing noise, the only voice possible to them, but which we fear makes less interesting their somewhat unprepossessing features.
A scale-like covering, which is fixed and immovable, covers the eye of the serpent, as shown in Fig. 4, and gives to it, as Prof. Nicholson vividly expresses it, the "peculiar, stony, unwinking stare" for which they are remarkable, and which, when they are enraged, becomes intensely fierce.
This covering is evidently transparent, as the animal distinguishes forms, but in the cast-off skin it is translucent only. Behind the eye-ball is a lachrymal gland, with a duct which conveys tears to the membranes of the eye. By this means they are kept moist. A conduit connects the eye-cavity with the olfactory opening, and, should the creature shed tears, it would be through that opening, not directly from its eyes.
In common with other animals, serpents have some habits and instincts peculiar to themselves, which are directly related to the necessities of their being; but we are not aware that they display great sagacity, cunning, or wisdom. They are not fertile in devices, not especially artful, and the extreme simplicity and smallness of their brain indicate their low mental powers.
The entire tribe of serpents for the purposes of this paper may be divided into the venomous and non-venomous species. Of the non-venomous, we will pass, with one or two remarks, the interesting families of double walkers, and slow or blind worms (Fig. 14), types which are structurally intermediate between true serpents and lizards. The first of these derives its name from the fact that it can progress
with facility forward or backward; the second from the erroneous notion that it has no eyes. To this class belong the curious glass-snakes, so named from their fragility. Other non-venomous serpents comprise the inoffensive and harmless, and some of the most terrible species. Of these we have noticed the gigantic rock-snake or python of India, which attains a length of 30 feet. The Natal rock-snake is found 25 feet long. Of equal size is the boa-constrictor of tropical America, formerly an object of worship. The anaconda, or water-serpent, which frequents the rivers of Brazil, and watches for its prey along their banks, is sometimes more than 25 feet long. These are among the most powerful of their kind, in whose folds man is helpless, and bones of goats and cattle are broken with a crash which, it is said, may be heard many rods. We turn from these, whose fearful presence we associate with the splendors of tropical forests, to species harmless and often serviceable to man, yet everywhere persecuted by him. Among these we find the beautiful ring and grass snakes of our gardens; the milk and striped or garter snake; the common adder (so called), but entirely harmless; the active black snake or racer, found nearly everywhere in the United States. More dreaded because more dangerous than the gigantic species mentioned, are the venomous
serpents, not powerful in strength or immense in size, but fierce in some cases, and in their attack deadly. The largest of these is said to be the bush-master, found in British Guiana, which, on the authority of Waterton, attains a length of fourteen feet. But the belted hamadryad of Burmah is often seen twelve to fourteen feet in length, and is a foot in circumference; and it is stated that specimens have been seen three fathoms (eighteen feet) long. If so, it is probably the largest known venomous serpent. This terrible creature feeds on other snakes, hence its scientific name, Ophiophagus elaps. Others, as the cobra and the rattlesnake, are relatively small, rarely attaining a length greater than six feet, usually not more than four feet.
But the distinguishing feature of venomous serpents is their poison fangs and glands, by which the fatal fluid is secreted. They kill by a stroke, or blow, which drives the fang into the flesh, and there discharges the venom. Some are intensely active and fierce, and will spring upon the traveler, as the fer de lance and the haje. Others, as the northern rattlesnake, seldom attack but rather retreat from man.
The fangs are in the upper jaw, as shown in Fig. 4. In a rattle-snake, four feet in length, they are about half an inch long. Behind them are the glands, which secrete the poisonous fluid, from five to ten drops of which have, in some cases, been obtained from a single fang. It is tasteless, and nearly colorless, and, on being dried up, leaves minute crystalline spicules, or scales. The venom of all the poisonous species of serpents appears to be essentially the same, but differs in intensity or virulence. The fang is perforated by a small canal in
front of the usual pulp-cavity, through which the venom is discharged by pressure brought to bear upon the glands from the act of striking. A rattlesnake confined in a cage, when irritated, struck against the wire bars with its fangs, throwing the venom a distance of three feet. The fang usually lies flat, and partly hidden in the fleshy tissue, but is erected when needed for use; and it is only when erected that its connection with the venom-gland is so adjusted that the fluid may be thrown out.
The poison is always more or less dangerous to animal life. Cattle have died from a bite of the fer de lance in a few hours. Smaller animals die directly. Horses have been killed by rattlesnakes, and people bitten by them may die in a few minutes or in a few days, but sometimes recover. If the poison is discharged into the arteries or veins, the vital functions directly fail, "the victim staggers, and falls from exhaustion—depressing gloom settles on the features—a cold sweat comes upon the face—and death at once supervenes." In such cases the blood is unchanged, and appears healthy; but, where the effect is not immediate, it undergoes change—"ceases to coagulate, the fibrine disappears, and the patient dies with ordinary symptoms of slow poisoning."
A multitude of remedies have been suggested for the bite of serpents; of these, ammonia and alcohol are prominent. Prof. Halfourd, of Australia, reported the recovery of seventeen out of twenty cases of severe bites, from the injection of a solution of ammonia into the veins. The free use of alcohol in some form has been stoutly advocated by many physicians, while others assert that patients have died from the poison even while intoxicated by the remedy. An exhaustive paper
on rattlesnake-bites, and their remedy, by Dr. Mitchell, was published in No. 12 of the "Smithsonian Contributions to Knowledge," to which we are indebted for several interesting statements, and to which we refer our readers.
The conclusions of Dr. Fayrer, from his exhaustive experiments upon snake-poisoning in India, are, that most of the popular remedies are of little value, and he seems to differ somewhat from Prof. Halfourd. The celebrated snake-stones, which are said to "absorb and suck out the poison," he "believes are perfectly powerless to produce any such effect." He advises ligature to prevent, if possible, the passage of the poison into the circulation. Whiskey and ammonia are useful as stimulants; but he found, by experiment, that neither liquor ammoniæ nor liquor potassæ destroys the poisonous properties of the venom, although mixed directly with it. Suction of the wound is good, but may be dangerous. Immediate cauterization of the wound, or removal of it by the knife, is indispensable.
It was found, by Dr. Gilman, that healthy, vigorous vegetables perish in a few hours on being inoculated with the venom of the rattlesnake. Others have found the same results, although Dr. Mitchell did not. Dr. Salisbury poisoned eight lilac and other bushes, the leaves of which above—not below—the point of inoculation withered in a few days. Terrible and virulent as this poison is, it undergoes decomposition in a short time, and becomes filled with forms of animal life and covered with fungi. It may, when fresh from the fang, be swallowed by the animal itself, or by man, without injury. Prof. Baird says: "I have myself (rather foolishly, I must confess) swallowed nearly the entire contents of one gland of a large rattlesnake;" but, if the animal be inoculated by its own venom, it speedily dies. Such, however, is not the case with the venom of the cobra, according to experiments made by Dr. Fayrer, who says: "I believe that it is
capable of absorption, through the mucous and serous membranes with which it is brought into contact. Placed on the conjunctiva of dogs, the symptoms of poisoning were rapidly developed." The same authority states that the cobra does not die from its own bite, or that of its kind, but that innocuous serpents are directly killed by it.
It is a singular fact that the flesh of animals killed by snake-poison may be eaten with impunity. The fowls killed by Dr. Fayrer were taken and eaten by the sweepers. But the blood of an animal killed by snake-venom is itself poisonous, and poisons the animal into which it is injected. The authority just quoted says: "I have transmitted the poison through three animals, with fatal results."
The formation of rattles upon the tail of a rattlesnake is a curious phenomenon. The notion that one is developed each year is incorrect. Young ones have been known to have six or more; sometimes two or three appear in a single year. The number seldom exceeds fifteen. The skin of one that was six feet long, now in the Museum of the Long Island Historical Society of Brooklyn, has fourteen rattles. De Kay cited, in 1842, the Clarion newspaper, published at Bolton, New York, which stated that two men killed, in three days, in the town of Bolton, at Lake George, 1,104 rattlesnakes, some of which carried fifteen to twenty rattles. They were killed for their oil. The same author states, on the authority of the Columbian Magazine for November, 1786, that a rattlesnake was killed, having forty-four rattles, which seems an incredible number. The use of the rattles is a subject of discussion. They are evidently well developed — not rudimental merely — and the conclusion is irresistible that they are of service to the creature. We cannot suppose that organs which are constant in a class of animals, could have originated, if entirely useless and unserviceable to it. Prof. Aughey suggests that the whirring rattle is a call-note by the animal to its mate. That it was thus used on one occasion he was an eye-witness. Again, it may be used to terrify its enemies; or to paralyze its victims with fright, or to call assistance in danger. He says: "I once witnessed an attack by seven hogs on a rattlesnake. Immediately the snake rattled, and three others appeared; but the hoses were victorious."
The power of serpents to overcome birds by fascination is considered by most writers doubtful. But it cannot be questioned, we think, that birds sometimes become powerless in the presence of snakes. We once saw a cat-bird on a low branch with drooped wings, feathers erect, and mouth open, apparently breathing heavily, looking directly at the head of a black snake which was within fifteen inches of the head of the bird, and very slowly moving forward. A sharp blow on a board startled the snake, and seemed instantly to release the bird from its dream, when it flew away. Perhaps the able paper on "Hypnotism in Animals," by Prof. Czermak, published in The Popular Science Monthly for September, 1873, may suggest a possible solution of this phenomenon.
All serpents are essentially oviparous; that is, the young are produced from eggs. Nevertheless, many species, including all the venomous ones, according to Cuvier, bring forth their young alive; but this is in consequence of the eggs being hatched before being laid. A boa constrictor produced both eggs and living young in the Zoological Gardens at Amsterdam. The eggs of serpents are without a calcareous shell, and those of our common species are often exposed in turning the ground in fields and in gardens. The young are at once quite active, and we have seen them when very young display the instinctive habits of their species.
The python coils around her eggs, and faithfully remains there during their two months of incubation; the temperature of her body rising, in one instance, to 96° Fahr. All this time she refuses food, " but appears feverish, and drinks water freely."
The time when serpents first appeared upon the globe is comparatively recent. No fossil remains of them have yet been discovered, until after the close of the Age of Reptiles. The oldest yet found were in the Eocene of the south of England. Prof. E. D. Cope first found them in the United States in the Eocene of New Jersey. They have been found also by Prof. Marsh in the Eocene of Wyoming. Prof. Cope discovered five new species during the past summer in the Miocene of Colorado, and has also obtained them from Post-Pliocene formations. So it appears that, during the whole of the Tertiary, serpents abounded, and the fact that in the Eocene they were so widely distributed suggests a much earlier origin for this order of reptiles. How numerous they may have been during periods subsequent to their advent is not easily determined. But, notwithstanding their abundance in the tropics, and in contiguous regions, it is probable that their period of greatest abundance, if not of greatest development, has passed. Civilization destroys them, or drives them to the swamps, the mountains, and the wilderness.
The number of species of snakes found in the State of New York is seventeen. Two of these are venomous, the rattlesnake and the viper. Sixteen species are named in Prof. Cook's catalogue for New Jersey, and that gentleman remarks: "All of them are of great value to the agriculturist, and the popular prejudice against them should be done away with." It should be more widely known and more often considered that snakes destroy immense numbers of animals which are detrimental to the interests of man, as rats, mice, insects, larvæ, and worms of various kinds. The fer de lance infests the sugar-plantations of some of the West India islands, not to destroy men, who fear it, but to obtain rats for food, which swarm there in incredible numbers. In the State of Maine are ten species of snakes, in Michigan fifteen species, and from Baird and Girard's catalogue, published in 1853, we learn that 119 species of North American serpents were at that time known and described.
In the older settled portions of the United States their numbers have diminished, and in the more thoroughly cultivated sections of New England, New York, New Jersey, and perhaps other States, their scarcity is a matter of common observation. Before persistent warfare, and amid conditions which are becoming more unfavorable to their habits of life, they will doubtless become fewer in number and species, and, in such regions, the period of their extinction may not be very remote.