EDINBURGH MEETING. 
465 
tion of the chief symptoms which are characteristic of the action of chloral, we are in¬ 
debted to Liebreich and to Dr. B. W. Richardson. 
Action of Chloral on the Lower Animals .—Frogs are usually rendered insensible by 
doses of half a grain of the hydrate of chloral. Fishes may, as it appears from Dr. 
Richardson’s experiments, be thrown into a sleepy condition by the subcutaneous in¬ 
jection of the substance. 
Birds are very easily affected. 
I am now about to inject two grains of hydrate of chloral, dissolved in thirty minims 
of water, under the skin of a pigeon weighing thirteen ounces. In a very few minutes 
the bird will become drowsy ; it may pass into a condition undistinguishable from that 
of natural sleep, or it may actually tumble upon its side, and remain motionless for a 
considerable period. (The lecturer having performed the experiment, the pigeon soon 
fell into a condition of placid sleep, and remained motionless during the rest of the 
evening.) 
I shall illustrate the action which this substance exerts on rabbits by injecting fifteen 
grains, dissolved in a drachm of water, under the skin of one of these animals. Soon 
the animal will exhibit disinclination and even disability to move, and then we shall 
find it passing into a condition of very deep insensibility. Unless the dose be too large 
the heart will continue to act, and the respiration will go on, and the insensible rabbit 
will awake from its deep slumbers apparently unaffected. If we observe the tempe¬ 
rature in animals subjected to hydrate of chloral, we find, as Dr. Richardson was the 
first to point out, an extraordinary fall of the thermometer, which again commences to 
rise when the symptoms begin to disappear. 
When given in doses of from thirty grains to one drachm, hydrate of chloral produces 
in man the same order of events as have been noticed in animals. A deep sleep readily 
follows its use, and this is not usually succeeded by headache, nausea, or the other dis¬ 
agreeable symptoms which not unfrequently supervene after the effects of narcotic drugs 
have passed off. 
It would obviously be unsuitable for me to discuss in this place the precise physiolo¬ 
gical action of this drug, even were our knowledge sufficiently complete to enable me to 
do so. I may, however, just mention some arguments which appear to me to render 
Liebreich’s hypothesis, of the action being due to the gradual development of chloroform 
from chloral, highly improbable. 
It is quite true that caustic alkalies induce the decomposition of hydrate of chloral, 
but the blood does not contain any of these substances ; and it is interesting to inquire 
whether the alkaline salts which do exist in blood, and upon which its alkalinity de¬ 
pends, are capable of effecting the decomposition of hydrate of chloral. 
This alkalinity is due, no doubt, chiefly to alkaline phosphate of sodium; in addition, 
the blood probably contains some bicarbonate of sodium. Now are these salts capable 
of decomposing chloral ? With regard to the first, I find that even when it is heated to 
boiling-point in contact with a solution of chloral, it fails to decompose it, while with 
regard to the second, I find that it is only after the temperature has been raised above 
70° C. that chloroform is given off, the evolution becoming extremely free when the 
liquid is boiled. Chemical facts therefore appear to me to militate against the chloro¬ 
form theory, which also is, I think, opposed by a consideration of the physiological ac¬ 
tions of chloral and chloroform. 
In the first place it appears to me that the symptoms which are produced by small 
doses of chloral are quite out of proportion with those which we can suppose would be 
caused by an equivalent quantity of chloroform existing in the system. In the case of 
a deep sleep, lasting for six hours, and following a dose of forty grains of the hydrate 
of chloral, we must, if we espouse Liebreich’s theory, suppose that twenty-six grains of 
chloroform are sufficient to account for the result. We must, namely, admit that the 
evolution of chloroform in the blood, at the rate of four grains per hour is capable of 
producing deep sleep. Now, when we think of the absence of sleep which is constantly 
noticed immediately after a patient has recovered from the anaesthetic effects of chloro¬ 
form, we cannot help being sceptical. In these cases the blood is often saturated with 
chloroform vapour, which continues to be excreted by the lungs for some time after, 
and yet there may be no tendency to sleep. 
If we contrast the action of chloroform and chloral, we find evidences of very great 
differences. In the former instance reflex action is soon abolished; in the latter, it ap- 
