HYDROCYANIC ACID. 
213 
§§ 266, 267.1 
menters ; and it is universally acknowledged that, although with strong 
doses of hydric cyanide injected into the circulation—or, in other words, 
introduced into the system—in the most favourable conditions for its 
speediest action, death occurs with appalling suddenness, yet that it 
takes a time sufficiently long to admit of explanation in the manner 
suggested. This has forensic importance, which will be again alluded 
to. Experiments on animals show that a large dose of a dilute acid 
kills quite as quickly as an equivalent dose of a stronger acid, and in 
some cases it even seems to act more rapidly. If the death does not 
take place within a few minutes, life may be prolonged for hours, and 
even, in rare cases, days, and yet the result be death. Coullon poisoned 
a dog with prussic acid ; it lived for nineteen days, and then died ; but 
this is quite an exceptional case, and when the fatal issue is prolonged 
beyond an hour, the chance of recovery is considerable. 
§ 266. The length of time dogs poisoned by fatal doses survive, gener¬ 
ally varies from two to fifteen minutes. The symptoms are convulsions, 
insensibility of the cornea, cessation of respiration, and, finally, the heart 
stops—the heart continuing to beat several minutes after the cessation 
of the respirations. 1 When the dose is short of a fatal one, the 
symptoms are as follows :—Evident giddiness and distress ; the tongue 
is protruded, the breath is taken in short, hurried gasps, there is saliva¬ 
tion, and convulsions rapidly set in, preceded, it may be, by a cry. The 
convulsions pass into paralysis and insensibility. After remaining in 
this state some time, the animal again wakes up, as it were, very often 
howls, and is again convulsed ; finally, it sinks into a deep sleep, and 
wakes up well. 
Preyer noticed a striking difference in the symptoms after section of 
the vagus in animals, which varied according to whether the poison was 
administered by the lungs, or subcutaneously. In the first case, if the 
dose is small, the respirations are diminished in frequency ; then this is 
followed by normal breathing ; if the dose is larger, there is an increase 
in the frequency of the respirations. Lastly, if a very large quantity is 
introduced into the lungs, death quickly follows, with respirations 
diminished in frequency. On the other hand, when the poison is 
injected subcutaneously, small doses have no influence on the breathing ; 
but with large doses there is an increase in the frequency of the respira¬ 
tions, which sink again below the normal standard. 
§ 267. Symptoms in Man. —When a fatal but not excessive dose of 
either potassic or hydric cyanide is taken, the sequence of symptoms is 
as follows :—Salivation, with a feeling of constriction in the throat, 
nausea, and occasionally vomiting. After a few minutes a peculiar con¬ 
stricting pain in the chest is felt, and the breathing is distinctly affected. 
Giddiness and confusion of sight rapidly set in, and the person falls to 
1 N. Grehaut, Compt. Rend., t. cix. pp. 502, 503. 
