have already adverted. Certain organs will, therefore, require to be particularly examined, and among these especially the liver and the bladder, or, rather, the contents of the latter.

Mr. Robo has favourably noticed my mode of detecting arsenious acid; but he has not referred to the two forcible objections against the employment of Marsh's test; namely, that both zinc and sulphuric acid, when commercial, often contain arsenic, and sometimes they are only with extreme difficulty procured in a state of purity. The history of the circumstance which led to my employment of the process which has been largely approved of by scientific men may not be uninteresting. It so happened that, when about to examine the contents of a stomach taken from a horse

supposed to have been poisoned by arsenic, I first tested the hydrogen which was being very abundantly given off by Marsh's ingenious apparatus; and the result was, that I obtained a number of metallic films, which proved to be arsenicum. Conjecturing the source, as none of the suspected solution had been yet introduced, I sent for fresh zinc and sulphuric acid, hoping they would be pure: still Marsh's test gave proof of the presence of arsenic. Again I changed the materials, but with the same result. I now felt myself in a difficulty, when it struck me that the solution might be decomposed by other means; and hence I was so fortunate as to apply a process by which the result is placed beyond the possibility of error.

Mr. Robb has stated, that my process obviates the necessity of employing zinc. It is true, at first I only asserted that metal was, by my plan, no longer required; but then I had obtained only half the desired end; for sulphuric acid is often even more highly contaminated with arsenic than zinc is. I confess that I have found no substance conduct electricity so well as dilute sulphuric acid; but the salts of potassa are sufficiently good conductors, and thus I have done away with its use, and therefore no objection can be advanced with regard to the materials employed, galvanism being my decomposing agent.

Mr. Jekyl drew attention to the assertion made by Liebig, that lead was only poisonous in the form of carbonate; and if the formation of this in the system were prevented, or if its decomposition within the system were effected by the administration of

acetic acid, so as to produce the acetate of lead, no fatal consequences would ensue.

Mr. Morton remarked, that the same fact had been asserted by Professor Thomson; and in proof that large quantities of the salts of lead might be administered with impunity, he stated that he had given to the horse four ounces of the acetate, and one pound of the diacetate of lead, without destroying life in that animal, or producing any very marked action beyond that of a sedative.

Mr. Robb observed, that some toxicologists, among whom was Raspail, considered the acetate as the most poisonous of the compounds of lead, and inquired of Mr. Jekyll what facts had induced Liebig to make this statement.

Mr. Jekyl replied, that Liebig had drawn his conclusions from experiments made upon dogs.

Mr. Morton said, that the presence of the phosphates in the stomach of the dog seemed to render such conclusions doubtful, as the phosphate of lead, which would be then formed, was a comparatively inert compound.

Mr. Robb.-The circumstance that the zinc and sulphuric acid of commerce both frequently contain arsenic, certainly does, as our worthy Secretary observes, give rise to difficulties in the employment of Marsh's apparatus; and these difficulties are, probably, not the less experienced by the great majority of medical men, who are but indifferent chemists. I have frequently, however, found both zinc and sulphuric acid of commerce in which no arsenic could be detected by Marsh's apparatus; and even if it were not so, it is in the power of any one to provide himself with these substances in a state of sufficient purity, and no chemist who undertakes such investigations should be without them. Although, therefore, Mr. Morton's process, even in so far merely as it gets rid of the abovenamed difficulties, is a very beautiful process, and is well worth the consideration of the scientific community, yet I conceive it is still more highly to be recommended for the reasons I have mentioned in my paper, viz. that the liquid under investigation no longer becomes contaminated by zinc, even in a state of purity, which is necessarily introduced in the employment of Marsh's apparatus, but which, under Mr. Morton's plan, is altogether dispensed with. It is almost unnecessary to

say, that this improvement, which admits of the examination for arsenic without adding to the liquid metals which themselves might have been administered as the poisonous agent, is a point of great importance gained.

Mr. Ernes noticed the unfitness of the dog for experiments whence any deductions of real value to the veterinary surgeon could be drawn. Neither one class of animals nor isolated facts were sufficient to establish truths connected with this important subject; but a series of experiments are called for, and the repeated observance of effects produced on all, or nearly all, animals could alone establish the definite action of any medicinal sub

stance.

FEBRUARY 11th, 1845.

The PRESIDENT in the Chair.

Mr. HALL gave the history of two cases of fractured pelvis in the horse, the result of the animals slipping down on the wood pavement. A similar instance was related by Mr. H. Daws, who also exhibited a fracture of the basilar process of the occipital bone of a horse, caused by the animal's rearing up and falling backwards; and two fractured pastern bones, one recent, the other having existed for some little time, in which the attempts made by Nature to effect a reunion of parts, was beautifully shewn.

An Elaborate Essay by Mr. JEKYL was then read “ On the AnTIDOTES AND TESTS FOR THE POISONS TO DOMESTICATED ANIMALS."

[We regret that want of space precludes the introduction of this Essay, and also some others, since it contains much valuable matter. Its consideration occupied this and the following meeting. Mr. Jekyl lucidly demonstrated the manner of applying the many tests for the different poisons, describing the chemical changes that take place, and the precautions necessary when organic fluids are being operated upon. We may recur to this subject, and give some extracts from the thesis to shew the progress that is being made in the acquirement of scientific principles by those who are about to become practitioners of veterinary medicine. Some of our readers may think that the subject was anticipated

by the " OBSERVATIONS" of Mr. Robb. Such, however, was not the case. The two essays constituted an admirable whole, Mr. Jekyl's, being an addendum, and filling up an important hiatus which otherwise would have existed.]

TUESDAY, FEBRUARY 25, 1845.

Mr. W. C. CRABBE, V.P., in the Chair.

CASE OF OSSIFIED TUMOUR ON THE PLEXUS CHOROIDES.

By Mr. Cox.

Mr. Cox.-The portion of a tumour upon the table was taken by me from the lateral ventricle of the brain of a horse which died in my infirmary. The animal had been seen frequently to turn round and round when at grass, and when put to work was as frequently observed to reel. Still he was able to perform his labour, and the less attention was, perhaps, paid to these symptoms as the appetite remained unimpaired. One evening, however, when returning from a neighbouring coalpit, the symptoms suddenly became more aggravated, and in consequence of this the owner sent the horse to my infirmary for treatment. The peculiarities that presented themselves were, pulse accelerated, and to be felt only at the heart. Breathing quick and laboured. Visible mucous membranes of a purple hue. When in the paddock the animal kept turning round and round, and when the head was elevated, he fell; and after struggling for a short time got upon his legs again with difficulty. He was almost continually yawning, and sometimes the respiration was so much impeded as to simulate roaring. The sound was such as I never heard before, and so loud as to be audible at a considerable distance. The skin was wet with perspiration.

When he was first brought in, I considered him to be in a dying state, and he only lived till the following morning. I was absent from home when death took place, and by the time I returned the owner had employed a man to skin the horse, which was not only

accomplished, but the brain was likewise exposed. Within the left ventricle was found a substance which Mr. Morton has correctly pronounced to be granular, attached, and about the size of a pigeon's egg. No other part of the frame exhibited any signs of disease except the lungs, which were slightly congested.

Mr. Morton.-Analogous cases to that which Mr. Cox has favoured us by relating are recorded in the Proceedings of the Association. Here is a specimen, taken from the museum, of a very large tumour involving the plexus choroides, and in the same collection is another and similar one. Cases of this kind are full of interest, and although they possess no novelty, yet, as establishing the susceptibility of the horse to a particular kind of cerebral disorder, are deserving of record. They are likewise of importance, as illustrating the extent to which such a form of disease may proceed. Both the horses, from which the specimens to which I have alluded were taken, died phrenitic; but we cannot for an instant suppose that the development of the tumour was simultaneous with the manifestation of the symptoms. There is more reason to think that the deposit resulted from long-continued abnormal action, and to regard it as the growth, perhaps, of years; and, being gradually developed, it caused little derangement till some exciting cause co-operating produced those symptoms which suddenly terminated the existence of the animal. These concretions consist principally of the phosphate of lime with animal matter. Every part of the frame is subject to tumours of this kind, and, when we reflect on the composition of the brain, there is certainly no reason why this organ should be exempt from them.

Two CASES OF SUPERNUMERARY TARSAL BONES.

By Mr. Cox.

Mr. Cox.-As every thing connected with the horse possesses interest to us, perhaps I may be excused for directing your attention to a circumstance which has not, I believe, been previously noticed. I have here the tarsal bones which belonged to two horses, and in each is found an extra bone, there being what, for the sake of description, I may call two small cuneiform bones in