minute, it rose, and did not appear to suffer the least from the injection; the introduction of ten grains more into the veins, gave rise to similar symptoms; the animal fell, but was again on its legs thirty seconds after the injection, the action of the salt being apparently due to its contact with the nervous tissue, and passing off as soon as blood which does not contain the salt, becomes again circulated over the nervous centres. Some minutes after the injection, the hind legs appeared to be partially paralysed, and after this had passed off, first one fore leg, and then the other, appeared to suffer in the same manner. Introduced into the veins in larger quantities, these salts appear to deprive the animal of the power of controlling its own movements; the whole body becomes violently convulsed; these convulsions very much resemble those produced by strychnine, and like these, can be called out by the slightest jar or noise; the respiratory movements remain unaffected, and the sensibility appears unimpaired, even in the midst of the strongest convulsions. In two instances, after death produced by the salts of ammonia, I have observed a sort of convulsive movement of the left auricle, which was in violent motion, without, however, causing any regular contraction, the movement seeming to part from many distinct points.*

Potass.-The accounts I have already published of the action of the salts of potass, (see Arch. Gen. de Med. Nov. 1839), will enable me to pass them over, with but a slight notice of their action on the vascular system. In this respect they exactly resemble the salts of ammonia, producing the same action on the general capillaries, and on the heart; both these substances appear also not to exert the least action on the lungs. In their action on the nervous system, there is a marked difference between the salts of potass and those of ammonia,—the violent convulsions which follow the introduction of the latter class of salts into the veins, never being observed when the salts of potass are injected. After the injection of six grains of the bicarbonate of potass into the veins, I have seen the animal fall on its side, the posterior extremities slightly convulsed, and after a few seconds again rise. On introducing an additional quantity of the salt, the heart was arrested, the salts of potass, after those of baryta, being the most fatal to the action of the heart.

Having now related the more important facts that have been. observed in my experiments, I shall conclude by offering one or two observations which they appear to suggest.

The most curious fact which a consideration of the above experiments presents to us, is the close connection which appears to exist between the physiological action of these substances and their

Convulsive movements caused by the injection of hydrochlorate of ammonia in. to the veins have been noticed by previous observers.

chemical properties. The property to which I more particularly allude is that of isomorphism. The analogy in the physiological action of isomorphous compounds, was first forced on my notice, by the perfect resemblance that exists between the salts of silver and of soda in their action on the animal economy when injected into the veins; differing as these salts do in their sensible chemical properties, but closely connected as being isomorphous. Farther investigation soon proved to me that this fact was of far more importance than I had anticipated, by showing that most striking points of resemblance exist generally beween isomorphous compounds in their action on the animal tissues, when introduced directly into the blood.* In the present state of chemistry, it would be useless to attempt to derive from this fact any farther generalization, for the doctrine of isomorphism itself is still in a very imperfect state.

Before quitting this point, I would recall an observation I made in a memoir read at the Academie des Sciences in June 1839, and which follows as a corollary from the fact of the analogous action of isomorphous compounds, although I had no idea at that time that such was the case. In speaking of the connection between the chemical composition of substances, and their physiological action, I observed-"Ce rapport n'est pas il est vrai tel que l'etat actuel de la science des affinités chimiques nous l'eut fait prevoir, car il est evident, que les decompositions effectuées dans le sang, par ces sels, decompositions sur lesquelles roule toute leur action physiologique, il est evident dis-je, que ces decompositions dependent de la base du sel, et ne sont que peu modifiées par la combinaison de cette base avec les acides, même les plus puissants." Should a more extended series of researches prove, that the identity which I have noticed in the physiological action of isomorphous compounds does not in all cases hold good, yet I think that the facts above related are sufficient to show that there exists some intimate connection between the chemical properties of substances, and their physiological action, the investigation of which promises to furnish a rich field for physiological researches.

* There is apparently an exception to this rule in the salts of lead, which, although agreeing with those of baryta and strontia, in most of the phenomena they present, yet exert an analogous action on the pulmonary tissue with the salts of silver, with which they are not isomorphous, but it has been remarked, that there exists a striking analogy in the combinations which the oxides of these two bases form with organic compounds; an analogy which does not exist between the oxide of silver and any other base. There is also a difference between the action of the salts of potass, and those of ammonia on the nervous tissue; for although these substances exert the same action on the heart and the systemic capillaries, yet the violent nervous symptoms that follow the introduction of the salts of ammonia into the veins are never produ. ced by the salts of potass. The peculiar action of the salts of ammonia on the nervous tissue, an action which connects it in its physiological relations with organic poisons, is interesting when we consider the chemical composition of ammonia, standing as it does between organic and inorganic compounds.

ART. VI. Contributions to Anatomy and Physiology; communicated at various times to the Anatomical and Physiological Society in Edinburgh. By R. Knox, M. D. Lecturer on Anatomy; Corresponding Member of the French Academy of Medicine; Fellow of the Royal College of Surgeons, and of the Royal Society in Edinburgh, &c. &c.

No. 1. On the occasional presence of a Supra-condyloid Process in the Human Humerus.

During the early period of the present winter, accident put at my disposal the entire carcase of a very fine specimen of the jaguar or American panther. It had belonged to the celebrated Carter, who exhibited here along with Mr Ducrow, displaying his astonishing command over animals whose natural ferocity of temper had led mankind very generally to suppose that such familiarity with the larger carnivora was not only fearfully hazardous, but even impossible to attain. During the course of the exhibition, Mr Carter's favourite jaguar died of acute inflammation of the right lung, and the carcase being of no use, was very kindly sent me by Dr Middleton, who obtained it from him for that purpose. In the course of the dissection of some of the more interesting points in the anatomy of this animal, I occasionally requested my class to examine those points for themselves, opportunities for doing so on so large a scale being very rare. I pointed out to them the elastic ligament supporting the claw in continual extension, excepting when acted on by the flexor muscles; but more especially I desired their notice to the presence of that foramen or hole in the humerus bone, a short way above the inner condyle, and formed apparently by a supra-condyloid process projecting from the shaft of the humerus downwards and forwards, until it unites itself to the condyle. Through this grooved hole or short canal, so formed, there passed the median nerve and humeral artery on their way to reach the bend of the elbow,—an arrangement which every comparative anatomist knows to be common enough in many mammals, and more especially in the carnivora. That such a structure should ever occur in man seemed somewhat unlikely; nevertheless, I was aware that the foramen had been asserted to be present by M. Majendie, if I recollect right, in certain Bosjemen skeletons, and if so, I presumed would be found to be formed by a supracondyloid process similar to what prevails so often in the carnivoIt happened almost at the same time that a friend had presented to me the cranium of a native of Polynesia,* and, think

ra.

A cranium belonging to one of the party who attacked and killed our immortal circumnavigator, Cook.

ing it a favourable occasion for making some remarks on the peculiarities of this and of some other human races, I submitted the cranium, together with many others, to the Anatomical and Physiological Society. As it is not my intention to reproduce what I said at that time respecting these races, I shall confine my remarks here strictly to what I then said respecting varieties in the form. and anatomy of the human humerus. These remarks were nearly as follow:

"Some physiologists had supposed that, in certain races of men, the humerus bone presented a form specifically different from others, as the yellow races of Africa, for example, quoted by M. Majendie, in which race it had been asserted that there existed a supra-condyloid process and foramen in the humerus. My own opinion was rather against this view as drawn from the humerus; first, because I did not believe the character to be a constant one, and secondly, because approaches to the same structure might be found in many European arms. In fact, several specimens of the humerus on the table of the society taken at random from my own museum, showed distinctly enough a short process, which, if accidentally elongated, as might happen in some individuals, would imitate very exactly the same conformation in the tiger, jaguar, &c. In the character of those specimens of the human humerus which possess a rudimentary supra-condyloid process, there was a remarkable circumstance to which I begged leave to call more especially the attention of the society: running from the process just alluded to, might be seen two ridges and a groove proceeding downwards towards the inner condyle. This groove, I ventured to conjecture, was for lodging the humeral artery and median nerve in those cases wherein the process accidentally possessed a considerable extent. I frankly admitted that I had never seen such a case, but felt confident that, happen when it would, the artery and nerve would be found to run behind and on the inner or ulnar side of the process, and would thus occupy the groove in question."

At the time I made this statement, I was quite aware that it was opposed to what we know of the usual course of the artery and nerve; but I felt assured, that either the analogy drawn by most German anatomists between this rudimentary process in man and the much larger one found in the carnivora, was well founded or it was not;* and if the former, that the course of the nerve and

These and such analogies are habitually carried much further by German than by sound British anatomists. A hasty glance at the plates of a German thesis by Dr Otto, would seem to show that he extends these analogies to the slight overlapping occasionally occurring in the bones of the human cranium; but I have not yet had time to examine his ingenious work with sufficient attention. It is quite true, however, that the bones of the human adult cranium do occasionally overlap each other, -occasionally thus imitating what we find to be a constant law in many species of quadruana and some other mammalia.

artery would be accommodated to this new osseous arrangement and follow the law of deformation as strictly as our structures obey usually the laws of formation. Now, it happened by a singular coincidence, that within two days after this communication was made to the society, a case actually occurred to bring the opinion to the test. The left arm of a stout muscular middleaged man was being dissected for demonstration at the morning lecture on the muscles, nerves, and arteries of the part. In the course of the dissection the pronator teres muscle was observed to have an unusually high origin; and on looking attentively at the structure, my assistant immediately called my attention to an anomaly corresponding strictly with what I had predicted two nights previously to the Anatomical Society, viz. the presence of a supracondyloid process : its connection with the inner condyle of the humerus by means of a ligament or aponeurotic expansion, and the consequent deviation of the main artery and median nerve from their usual course, in order to pass behind this process in the groove, half osseous, half ligamentous, thus formed, afterwards to return, a little lower down, so as rapidly to regain their usual relative position in the bend of the elbow; in short, the precise anatomy of the arm of the jaguar, with this difference merely, that in the latter the supra-condyloid canal is entirely osseous, whilst in man it is only partly so, the process not extending so as to unite itself by bone with the condyle.

The accompanying sketches will no doubt explain in a more interesting mode to all readers, the curious anomalies in the human arm of which it has been the object of this brief memoir to give some account.

Plate III. Fig. 1. Anterior view of the bend of the elbow (left arm) in an adult male; the preparation is in my possession. a. The biceps muscle.

b. The brachialis flexor.

c. The humeral artery in the lower third of the arm.

d. The median nerve.

e. The supra-condyloid process running from near the inner margin of the humerus downwards, and inwards towards the inner condyle; it measures about three-quarters of an inch in length, but does not reach the condyle by about an inch and a quarter.

f. A tendon or ligament running from the free extremity of the process to the inner condyle of the humerus, nearly parallel with the internal inter-muscular ligament, and united intimately with it, particularly below.

g. That portion of the pronator teres which usually arises from the anterior surface of the internal inter-muscular ligament, but which in this arm arose from the above described tendon, f.