Popular Science Monthly/Volume 42/March 1893/Notes on Paleopathology
|NOTES ON PALÆOPATHOLOGY.|
ANIMALS that lived during the past ages of the world, and now long since extinct, must have suffered, it would seem, from many injuries quite similar to those now sustained by their descendants of the present epoch. So far as the writer is aware, the discovery of the evidences of such conditions is of extremely rare occurrence, and the literature pertaining thereto practically a blank page. Among fossil invertebrate remains I do not recall ever having either observed or heard of a single instance, although during geologic times many forms of the invertebrata must have perished when such parts of their economies as usually fossilize exhibited evidences of disease, and would thus be observed by the paleontologist when those specimens came to be discovered and examined.
With respect to the vertebrata, however, I have been somewhat more fortunate in this matter, as I can show in the course of the present article. Still, even among them one may examine many hundreds of specimens before he will meet with one of their fossilized bones which shows that it was diseased at the time of the death of its owner. It is one of the very rarest of things. In two or three different articles, several years ago and later, I published a number of instances where, in the preparation of the skeletons of existing birds, I had discovered a variety of pathological conditions of the bones. Many, if not the majority of those cases, however, were the results of gunshot wounds, and, of course, it goes without saying that that class of injuries would not occur among fossils; and their very absence is one good reason for the greater rarity of examples of disease in the skeletons in these extinct forms, as one may easily imagine.
Several months ago Prof. E. D. Cope, of Philadelphia, placed in my hands for description some fifteen hundred specimens of fossil birds from the Pliocene of southwestern Oregon. Here then, indeed, was an excellent opportunity to investigate such a matter, for surely among several hundreds of bones we would be most likely to meet with, at least a few specimens of a character to which reference has just been made.
These fossils were principally of water birds, having been discovered in the former bottoms of dried-up Tertiary alkali lakes, or upon the margins of those undergoing a similar process. With them were found immense numbers of arrow points of human manufacture, and the question had arisen as to whether it were not possible that they had been shot at the game during former times. To shed further light upon such an interesting subject, I most carefully examined each and all the specimens to discover if possible any healed wounds (fossilized) that may have been produced by such means. My interest in this matter was much stimulated by what Prof. Cope had formerly written in the American Naturalist for November, 1889. After describing the discovery of the bird-fossils referred to above, that eminent paleontologist there says that "scattered everywhere in the deposit were the obsidian implements of human manufacture. Some of these were, of inferior, others of superior workmanship, and many of them were covered with a patine of no great thickness, which completely replaced the natural luster of the surface. Other specimens were as bright as when first made. The abundance of these flints was remarkable, and suggested that they had been shot at the game, both winged and otherwise, that had in former times frequented the lake. Their general absence from the soil of the surrounding region added strength to this supposition. Of course, it was impossible to prove the contemporaneity of the flints with animals with whose bones they were mingled, under the circumstances of the mobility of the stratum in which they all occurred. But had they been other than human flints, no question as to their contemporaneity would have arisen " (page 979).
Now, I found no fossilized injuries of the bones in question that could be attributed to wounds of them that arose from arrow-shot; but, on the other hand, one or two pathological conditions of interest were discovered, and one of these a fracture in the course of healing.
In order to make clear the stage at which this healing fracture existed at the time of the death of the individual that sustained it, I will first offer a few remarks upon the course of such injuries in existing animals.
Fractured extremities of bones in both mammals (not including man) and birds are rarely kept quiet and properly approximated during the healing process, which takes place at the fractured extremities. This results in the formation of a "provisional callus" which soon surrounds the broken ends of the bones, and acts as an osseous splint, that strengthens with time. For the first week or more this exudation of reparative material takes place at the point of fracture—occurring externally between the periosteum and the bone, and internally between the medullary membrane and the bone. At the end of about three weeks this provisional callus acquires a firmness about equal to that of cartilage; which, at the end of three months, both internally and externally, ossifies—the ossification being more or less of a spongy nature. Shrinkage now takes place, and this spongy ossification becomes modeled down, forming compact bone. Still, at this stage the fractured ends are only united by fibrous tissue, though the surrounding ossified callus holds them firmly together.
Finally, this provisional callus undergoes more or less complete absorption, and the permanent callus forms directly between the fractured ends of the bone. This results in the nearly complete disappearance of the periosteal enlargement, and, internally, in the re-establishment of the medullary canal. Normally, this is the course of the union of fractures in long bones, of the character referred to above, but there are a number of exceptions to it, and irregular unions occur which do not require comment from me in the present connection.
Several years ago I obtained a turkey vulture (Cathartes aura) that had survived a glance shot from a carbine ball which fractured both bones of the left forearm of the upper extremity. It had also sustained other fractures, all of which I fully described in the New York Medical Journal (see No. 3 of foot-notes given antea). This bird I subsequently killed with chloroform and prepared its skeleton. Upon examination it was discovered that the left ulna and radius were each fractured at the points shown in the accompanying cut (Fig. 1), and were at the time of its death at that stage of union where the provisional callus is well under way toward absorption.
From my various observations in such cases I have arrived at the conclusion that at this stage the weakest point in the provisional callus lies in the plane of the meeting of that material, as it is furnished by the two broken ends of the bone—in other words, it is at its thickest part and in the plane of the fracture. I mention this fact, as reference will soon be made to it again, further on.
Owing to the support afforded by the quill-butts of the secondary feathers of the wing in a bird, acting as a compound splint of Nature's furnishing, the radius and ulna in that class of vertebrates Fig. 1.—Left Ulna Radius of a Specimen of the Turkey Vulture (Cathartes aura.) Outer aspect, showing union three weeks after fracture from a shot from n·45 Government carbine ball. From the author's figure. (The larger bone is the ulna.)usually unite with scarcely any deformity. This is by no means the case in mammals below man, for in them, where the long bones of the limbs are fractured near their middle, or even in the upper and lower thirds, very considerable angularity results upon union—an angularity that in some cases may even equal a right angle, as I once saw in the case of a fracture of the femur in a muskrat (Fiber zibethicus). The specimen exhibiting the fracture in Prof. Cope's collection of fossil birds consists of a portion of some such bone as the humerus from a bird apparently about the size of a medium-sized goose. It is about 4·5 centimetres long, and has been broken longitudinally both through the callus and the shaft, the corresponding piece having been lost. If the piece be from the humerus of such a bird as I have mentioned, it must be from the very middle of the shaft, for it presents no part of the sigmoid curve as seen at either extremity. The walls are comparatively thin, and the medullary canal large. The fracture occurred square across, or at right angles to the axis of the shaft. There is no provisional callus within the medullary canal, but the bone in the neighborhood of the fracture within that tube is roughened, showing the effects of the attempt at repair. Probably the internal provisional callus may have been broken out of the specimen before it was discovered. Externally the fossilized, spongy, bony callus is quite abundant, and has all the appearance of the distal moiety of the callus upon the ulna of the turkey vulture shown in Fig. 1, and was at about that stage when the individual perished. Among existing birds of the group to which I suspect this specimen belonged, as the swans, geese, and ducks, I have known very excellent results follow in the case of the direct simple fracture of the shaft of the humerus. If they be not pursued to the death by the hunter, they usually swim about on the water during the day, and feed along the shore or in the marshes at night, always holding the wing well up until the fracture unites. The case is different with land birds, where, in getting about, the seat of the break is often violently disturbed.
|Fig. 2.—Left Carpo-metacarpus from the Hand of an Extinct Swan (Olor paloregonus) from Oregon. Outer aspect and natural size from the specimen by the author. a, the seat of the disease on the summit of the first metacarpal.|
This interesting fossil specimen, then, goes to prove that the union of fractures of the shafts of the long bones in the vertebrata during the later Tertiary times was identical with what now occurs in the case of existing forms. Such a thing would be most naturally suspected, but, as with some of the simpler, self-evident theorems in geometry, it is invariably required that the proof be forthcoming. It is quite another thing to conjecture how this fracture came about. If I be right in my guess that the specimen was a bird, and that bird was a goose, why, it may have been done in battle with one of its own kind; it may have been done by a blow from a bird of prey, which afterward failed to secure the quarry.
Such evidence as I possess upon the first-mentioned supposition is by no means to be implicitly relied upon; and in the case of the second supposition such a circumstance as is pointed at would certainly be one of the rarest occurrence.
The bone could much more easily have been broken by having been struck by an arrow by its flint-pointed head, provided it were shot with sufficient strength from a bow. Of the probability of that I leave the reader to judge for himself; there is some evidence to sustain such a conjecture, no inconsiderable part of which has been presented above, and more can easily be found between the lines.
I pass now to the consideration of one other pathological condition presented on the part of the bones of the fossil birds in Prof. Cope's collection. It occurred only in specimens of swans, geese, and ducks, and consisted in a more or less abundant exudation of spongy, osseous material that appeared upon the proximal part of the first or pollex metacarpal of the carpo-metacarpus (Fig. 2, a). It was present in a good many specimens of all the families enumerated above; it was entirely absent in a lesser number of specimens of two or three of the same groups. It would seem to me that such a condition could only be brought about by some blow or other given at the point in question, which point is one in the wing of those birds that is quite superficial, in so far as the bone is concerned, and might, upon receiving a square rap of sufficient force, injure its periosteum to such an extent as to have a subsequent osseous exudation result there. The vast majority of those fossil anserine birds of that region were identical with those species now in existence in our avifauna, and, it is but fair to presume, possessed habits similar to them. Yet in Pliocene time they may all have had some different habits: it occurred to me that they may have fought each other with their wings—or, may be, fought some common enemy as yet unknown to us. The fossil bones exhibiting this disease may have belonged only to the males, and they may have fought during the breeding season; or it may have occurred only in the females, who for some reason may have been called upon to fight with their wings in defense of their young. Some existing birds have large spurs upon certain bones of their hands, and they are known to fight with their wings at the present time; but in some future epoch, if the descendants of those forms persist, the necessity for such an armature may pass away, and with it the spurs themselves. Modern swans are known to strike a blow with their wings in defending themselves or their young. With these thoughts in my mind I asked Prof. Cope for his opinion in the premises, and, without hesitation or hint from me as to my own musings, he answered, "Why, possibly, they fought each other with their wings." I have never observed any similar pathological condition in our modern Anseres, and I have both made and examined skeletons of a great many of them.
- Palæopathology (Greek παλαιόσ, ancient, and πάθοσ, a suffering), the word used in the title of this paper, is a term here proposed under which may be described all diseased or pathological conditions found fossilized in the remains of extinct or fossil animals.
- The following are the principal articles of mine on this subject: (1) Notes on a Few of the Diseases and Injuries in Birds, The American Naturalist, vol. xv, April, 1881, pp. 283-285; (2) Notes on the Diseases of Birds' Beaks, The Journal of Comparative Medicine and Surgery, vol. viii, No. 2, April, 1887, pp. 181, 182 (illustrated); (3) Examples of Fractures and their Union in the Bones of Birds, The New York Medical Journal, vol. xlviii, No. 26, New York, December 29, 1888, pp. 714, 715 (illustrated).
- I am under obligations to the New York Medical Journal for the loan of the electro of this figure, and hereby tender my grateful acknowledgments for the same. The original was drawn by me direct from my specimen, a number of years ago, and I still possess the latter in my private cabinet.
- In the collection I discovered the remains of two new species of extinct eagles.