Popular Science Monthly/Volume 22/March 1883/Vivisection and Practical Medicine
|VIVISECTION AND PRACTICAL MEDICINE.|
By G. F. YEO, F. R. C. S.,
PROFESSOR OF PHYSIOLOGY IN KING'S COLLEGE.
OVER and over again we have been challenged by the opponents of science to give "one conclusive example where experiment has been of direct use to practical medicine." To any one familiar with the history of scientific medicine there can be no difficulty in finding numerous such instances, and, as a matter of fact, many examples have from time to time been given by various writers; but to make these cases satisfactory and conclusive to persons who know but little, and do not care to know more, of the true bearings of the question, is a very difficult matter. Such a test is totally wrong and misleading when applied to the utility of experiment on the lower animals. The matter must be viewed from a wider standpoint than that embracing only single instances of direct benefits accruing from specific experiments.
The primary object of experimental research is to advance physiology—the science which teaches us the uses of the various organs and textures of the body in the normal state, and how the working of the animal economy is carried on in health. The value of physiology depends on the knowledge it gives us of the normal operations of the body, and not on the few cases in which certain experiments happen to aid us in understanding disease, and thus directly promote the practice of the healing art. Our argument is rather this: Physiology is the foundation of both pathology and therapeutics, which together make up medicine; and therefore rational medicine depends directly upon physiology for its strong growth and genuine progress.
Now, physiology can not advance without vivisection; experiment on living animals is as essential to its progress (though far less general in application) as is dissection for the study of anatomy. Therefore, experimental research, including that carried out on living animals, is as necessary for the progress of the practice of medicine as is experimental research in any other science for its advancement and application to daily life. The immediate object of physiological experiment is, then, not to make out new practical methods of treating disease, but rather to attain to a more complete and sound understanding of those general laws which govern the actions of the living body in health—laws which must ever form the only firm basis of the knowledge of disease, and the only sure guide to judicious modes of treatment.
The rational practice of physic, as it is carried on in the present day, is in a great measure the outgrowth of a slowly growing physiological science, upon which it depends, and from which it can not be separated. There is hardly a thought that can strike a practitioner that does not in some way depend upon physiological facts which have been elicited by experimental research. I do not mean to state that the accurate and painstaking observation of clinical facts and postmortem appearances has not done much—probably more than anything else—to bring our medical knowledge to its present stand-point; but I contend that clinical observation and post-mortem experience without physiological research would never have been able to advance medicine to the position it holds in modern times; and, on the other hand, I believe that physiological study, even unaided, could arrive at a rational system of treatment. No doubt both clinical study and pathological observation have not only helped practical medicine onward, but they have also greatly contributed to the progress of physiology itself. In fact, I find it impossible to separate exact clinical and pathological work from scientific research of a purely physiological nature. Is not all treatment more or less experiment? And is not this particularly true of purely empirical treatment? Nowadays, where is the pathological laboratory in which a mere record of post-mortem changes in the human subject is not aided by experimental inquiry into pathological changes in the lower animals?
In assigning to each department of medical study its due meed of credit, their relative ages must be borne in mind. It has been asserted that all the improvements brought about by experimental research would have been introduced with equal certainty had experiment on living animals never been attempted. Observation, experience, and thought would have attained all the results we now enjoy. Possibly so; but when? Clinical observation can be traced back some three or four thousand years, and even then it started with a rich legacy of traditional knowledge. Experimental physiology as a science was only born about a hundred years ago. If we compare the progress made by medicine during the last hundred years with that of the previous thousand years, we shall be able to judge of the relative rates of progress of the two systems of working. The difference seems to me to lie in the fact that unaided clinical observation—that is, practically the empiric method—goes the wrong way about arriving at a conclusion. It says, Try this or that or the other remedy, and note which is successful. This is like a boy who will not systematically work out his sum in long division, but prefers to arrive at the quotient by guessing probable numbers one after the other, and multiplies them to see which is the right one; he may, after much trouble, by chance hit upon the correct answer, but he more commonly fails: and most probably the boy who works out his sum in the straightforward way will far sooner arrive at the desired result. Physiology moves onward by means of accumulating and arranging facts which have borne the test of experiment. Empiricism accumulates observations which, without further test, are used to formulate theories that, as likely as not, are unfounded, and are as apt to mislead as to advance medical knowledge. When asked to give an example of the utility of experimental physiology in the treatment of disease, I feel inclined to answer with another question: Is there one reliable system of diagnosis or one mode of treatment now in use which has not been modified or improved, if not directly suggested, by physiological knowledge? And I must certainly confess that I know none. Before attempting to bring forward single cases, as instances where certain experiments have been of direct use to medical and surgical practice, I shall examine the question from the opposite stand-point, by taking some simple case of every-day occurrence, and glancing at its routine examination and treatment. We can then see to what extent vivisection influences the practitioner in the details of his daily work. We may safely take a case at random; one not associated very closely in our minds with any brilliant experimentation will, perhaps, be the best. The following case, which I happen to have seen recently, will do as well as any other:
Not long since I found a policeman examining a poor woman who was said to have had a "stroke." She lay speechless and motionless on a door-step; she showed no signs of convulsions, no stertorous breathing, no frothing at the mouth. So the policeman hesitated to make a diagnosis—thinking, no doubt, that other causes besides a "stroke" might give rise to such a want of muscular irritability. Gently shaking her had no effect, but on his applying some form of stimulus to the finger she showed signs of returning consciousness, and the left leg and arm moved slightly. The right eye remained partly open, the other was closed; when the eyelid was raised, so as to expose the pupil to the sunshine, some movement of the muscles of expression was observable, but only on the left half of the face, to which side the mouth was slightly drawn. This became more obvious when some drops of cold water were thrown at her. The pulsation of the temporal artery was visible. Putting my ear to the top of her chest I found the heart beating violently, and heard a prolonged blowing noise instead of the sharp, clear tone of the second heart-sound. Without much effort my thoughts had passed from the pulsating temporal artery to the heart, and from the imperfect aortic valves to the middle cerebral artery, where I fancied an embolus must be impacted. I told the policeman the woman had better be taken to a hospital, which was done accordingly.
How was it that I was able confidently to advise the policeman about this poor woman, though he was no doubt very experienced in this sort of cases? What aid did experimental inquiry give me in arriving at my conclusion?
Well, in the first place, I knew that the paralysis was restricted to voluntary movements, without the motions belonging to organic life being in the least interfered with. Vivisections of the earliest times informed me that this was quite possible as a result of some injury of the nerve-centers, and experiments of more recent date enabled me to exclude a large part of these centers from being the seat of the lesion. That there was no local injury of the spinal cord in the dorsal region I knew, both from the loss of consciousness and from the fact that the reflex action of the lower limbs was not intensified, and vivisections informed me they would have become so had this been the case. I could see by the movement of the left leg that only one side of the body was paralyzed; and then the look of the face distinctly showed that part of the seventh cranial nerve, which Charles Bell's vivisections taught me to know to be motor in function, was paralyzed. This fact, together with the ready reflex action of the eyes and the sound side of the face, which I knew by vivisection required unimpaired sensory nerves, showed me that it could not be a case of profound toxaemia such as the policeman supposed to be possible. I knew by vivisections performed by many English physicians and physiologists, some of whom are still among us, that the second heart-sound depended on a certain action of the aortic valves. Not hearing the familiar sound, I concluded that the aortic valves must be diseased. Experiments on living animals concerning coagulation of the blood within the vessels informed me that when the lining coat of a blood-vessel, or the heart, is diseased, little clots are often formed at the diseased or injured part. I knew, further, from Virchow's classical experiments on living animals, that emboli introduced into the arterial blood-current often become impacted in the middle cerebral artery, and that the embolic blocking of a brain-artery, by shutting off the blood from the area it supplied, caused a sudden arrest of function of the part. Although the nerves going to the various paralyzed muscles arose from very different regions of the cord and brain, I know by vivisections that there is a part of the cortex of the brain the injury of which would cause them all to be powerless. Clinical observation and pathological anatomy would have informed me that it was probably a brain-lesion; but, had it not been for the light thrown by vivisection on the few facts I was able thus hurriedly to observe, I should not have been much wiser than any other by-stander, and could only have agreed with them that it was a "stroke" of paralysis.
Now let us consider a surgical case. The other day I mentioned some of the old methods of operation, when buttons of vitriol, caustics, steel compresses, boiling oil, hot irons, a copious receptacle for catching the blood, and elaborate machines, such as those on the table, were among the apparatus the surgeon had to prepare for operation.
Let us now turn to a modern operation, and let us consider whether our present modus operandi is influenced by the light which experimental inquiry has shed on physiology during the last century. I shall not attempt to recount any one of the numerous cases which the surgeon now approaches with perfect confidence of undoubted success, although a comparatively short time back they would have been looked upon as completely beyond his reach. Many such cases, which formerly would have led either to certain death, enduring misery, or life-long inconvenience, must occur to the minds of all here. Let us take a case of disease or injury requiring the amputation of a portion of an extremity. In the first place the patient is made quite insensible to pain by the administration of chloroform, or some such drug; not only is he insensible to pain, but also unconscious to all that he formerly would have been obliged to see and hear, by no means the least painful part of the operation. With regard to the use of anaesthetics, I shall not delay, for vivisection can not claim to be the sole means of introducing this great boon to modern surgery, although experiment on living animals played a most prominent part both in their discovery and their introduction into common use in this country, as has been frequently pointed out.
The next step in the operation is to make the part bloodless. This can be done in the following way: By holding up the limb for some time to facilitate the flow of blood from the veins, and thus to reduce the blood-pressure within these vessels, by which means the local vasomotor mechanisms are brought into play with considerable force, so as to reduce the quantity of blood in the limb, allowing only a limited flow to continue. Then Esmarch's elastic bandage may be applied to further empty the minute blood-vessels. By this means the textures to be cut into may be made to remain, during the active part of the operation, as bloodless as those of a corpse. The advantage of having no dread of hæmorrhage to induce haste, no blood to impede the view, or render the instruments difficult to handle, can hardly be overestimated. So that, even apart from the all-important point of preventing the weakly patient losing blood, this bloodless surgery must be regarded as one of the most important improvements in modern methods. And how far may it be traced to vivisection? We know that the contractility of the blood-vessels, and the high pressure of the blood in the arteries, as well as the motions of the heart and the course of the blood, were demonstrated by this means; and is not this the key of the whole matter? But, further, were we not familiar by vivisections, and by the removal of tissues from the bodies of recently killed animals, with the fact that the textures can retain their life and function for a considerable period after their normal circulation has ceased, who would have dared to suggest that the entire limb of a living man should be deprived of its blood during the time occupied by a tedious operation?
Then, with regard to the means of permanently arresting the escape of blood from the wounded vessels. We have no longer a receptacle for blood; indeed, the handful of sawdust on the floor that was fashionable when I began medicine is no longer used. John Bell, after giving a graphic and fearful account of the terrors of haemorrhage, says: "Is not this fear of hæmorrhagy always uppermost in the mind of the young surgeon? Were this one danger removed, would he not go forward in his profession almost without fear?" I do not think this fear ever crosses the mind of the young surgeon now, so rare are deaths from external hæmorrhage. I have never seen one death from such loss of blood in the twenty years that have passed since I first commenced to study medicine. Why has the dread of bleeding ceased to chill the heart of the surgeon when entering on an operation? Vivisection has not done all, but it has done much to help us to attain to this degree of excellence in our present methods.
The use of the ligature can be traced so far back in the history of medicine that it is impossible to say whether it was first used upon man or animals. Very definite accounts of it occur in the writings of the Arabians of the tenth or twelfth century. Although its value, or rather its great convenience, in military surgery was recognized and extolled by Ambroise Paré, the inestimable value of the ligature remained unknown in general practice for nearly a hundred years after his time. This was, no doubt, partly on account of the fact that experiment was not used to test its efficacy and mode of action until comparatively recently. By vivisections the chief errors in its application were by slow degrees removed, and now we rest almost exclusively on the improved method of tying arteries as the means of arresting the flow of blood from a recent wound. First of all, the nerves used to be included in the ligature. Vivisection showed the folly of thus attempting to confine the animal spirits, or nervous fluid, and practice proved that thus tying the nerves always caused excruciating agony, and often gave rise to fatal spasms (tetanus), which made ligature to be dreaded even by its warmest advocates. In the second place, the wide ligatures which were made of soft material and lightly tied over corks, etc., often failed to check the bleeding. Dr. John Thomson, of Edinburgh, was among the first who made experiments on this subject, and I believe much of the credit given to Jones really belongs to him. Following the precepts taught by Thomson, Jones also made numerous experiments on animals. He found that a hard, thin ligature, applied so as to cut the elastic inner coats and leave the tough outer wall of the vessel uninjured, was much more surely followed by a deposit of "coagulable lymph," and by more satisfactory occlusion of the vessel, than when one or several soft bands were tied lightly on it. This fact hardly gained the universal and complete confidence of surgeons until further vivisections performed by Lister, Brücke, and others, showed that the smooth lining of the vessel was the chief factor in preventing coagulation, and that intravascular clots are formed most readily when the lining of the vessel was injured and the blood ceased to move. Instead of timidly tying a loose knot for fear of injuring the vessel, the surgeon now ties a firm ligature so as to rupture its lining coat, or at least to apply sufficient pressure to cut off its nutrition and thus cause its death in order to make a starting-point for the coagulation which must occur to secure its permanent closure.
Another great objection to the old ligatures was the delay they caused in coming away. This wearied the surgeon and exhausted the patient. The ligature was sometimes pulled away before its time, and this often gave rise to the much-dreaded secondary hæmorrhage. In counseling that the ligature be left alone, Petit adds the remark, as a kind of consolation, that he finds them generally to come away of themselves in about two or three months. Of this sort of annoyance we hear nothing now. Experiment on the lower animals has taught us the existence of the lymphatics and their absorbing power. Experiments upon living animals has shown us that this power of absorbing extends to such things as catgut, a material readily made into strong cords. Properly prepared catgut is, therefore, almost universally used as a ligature, the ends are cut off short, and the knot is left to be absorbed, and never once thought of again.
And, lastly, the edges of the wound are brought together with stitches of silver wire, silk, catgut, horse-hair, according to whether much or little traction or more or less coaptation is demanded. Undue tension, compression, gaping, and irregularity of the wounded part, are all avoided; a means of exit for serous oozing, etc., is provided by non-irritating drainage-tubes. The antiseptic dressings are applied carefully and exactly. Large tents, dossils of lint, rude compresses are not thought of. The aseptic wound heals without swelling or inflammation. No throb disturbs the patient's rest. No drop of pus comes from the cut surface. Fever, tetanus, pyæmia, second hæmorahage, as well as the old dread of the bleeding during the operation, are all nearly forgotten.
To the minds of the surgeons of the last century such a method of operation and such a mode of healing would probably suggest the longed-for magic remedies by means of which many hoped to replace the cauteries, caustics, compresses, and filthy dressings with which they strove to heal the open wounds of their exhausted and cachectic patients.—Lancet.