118 REPORT—1843. 
These quantities, however, must depend, to a certain extent, on the size of 
the animal, and on the rapidity with which the injection is introduced. 
The marked and peculiar action which these substatices exert on the ner- 
vous system, and the entire absence of any unpleasant symptoms when they 
are injected in moderate quantities, suggests the idea as to how far this pro- 
perty might be made available against some of the more violent convulsive 
diseases, such as tetanus and hydrophobia, against which the resources of our 
art are at present so powerless. Should any cases of these diseases come 
under my care, I certainly should try the effect of injecting some of these 
substances into the veins. I think the acetate of magnesia might be the most 
useful salt to employ; its permanent effects when introduced into the blood 
do not seein at all deleterious, as I have kept dogs ten or twelve days without 
any ill consequences, after introducing in one instance fifteen grains, and in 
another twenty grains into the veins. I should consider that from two seru- 
ples to a drachm dissolved in two ounces of water, could not possibly be in- 
jurious if introduced into the veins of a human being, and probably a much 
greater quantity might be borne without danger. 
The only other class of substances with which I have experimented has been 
arsenic and phosphorus, which have been used under the form of arsenic, arse- 
nious and phosphoric acids. It is a curious fact, that arsenic, one of the most 
violent of poisons, should, when introduced into the veins, even in much larger 
quantities than would be required to produce death if given by the stomach, 
give rise to no particular action on any organ which permits us to localize its 
effects, or to say that it kills by the changes it produces in any one tissue in 
preference to another. It certainly does not kill by its action on the heart, for 
when as much as twenty grains of arsenic acid are introduced into the veins, 
the action of the heart is but very slightly affected. Nor are the functions of 
the brain at all interfered with by so large a dose, at least not for some time. 
It would seem that it is not on any organ in particular that the poison acts, 
but that the whole of the tissues of the animal gradually lose their vitality, by 
changes which appear to require time for their production. After death, the 
mucous membrane of the lungs and the intestinal canal are the parts which 
present the most marked effects of the action of the poison, but the amount of 
lesion of these parts is often not sufficient to produce death. The similarity 
of action of the arsenic, arsenious and phosphoric acids is such, that I shall only 
give a detail of some experiments made with the former of these substances. 
On injecting a solution containing three grains of arsenic acid, dissolved in 
six drachms of water, into the jugular vein of a dog, there was a diminution 
of pressure in the arterial system, as indicated by the hemadynamometer ; 
after a short time the action of the heart became quicker, and the pressure 
in the arteries again increased ; the functions of the nervous system did not 
appear deranged: on again injecting six grains the same phenomena pre- 
sented themselves ; the respiration, however, was now becoming very rapid, 
and this was the only marked symptom, when two other injections, one of four- 
teen and the other containing forty grains of the acid, had been introduced ; 
at this time, however, the action of the heart had become much weaker, and 
the pressure in the arteries was only equal to a column of mercury of two 
inches ; sensibility appeared unimpaired, and there were no convulsions. On 
again injecting sixteen grains of the acid, the action of the heart ceased after 
a few seconds. A post-mortem examination showed that both the mucous 
membrane of the lungs and intestinal canal had been much affected by the 
poison; they were both reddened, and were covered with a frothy secretion, 
which in the lungs must have greatly interfered with the arterialization of the 
blood. In another experiment a drachm of the acid was injected at once, 

