PHYSIOLOGICAL ACTION OF NITROBENZENE VAPOR ON ANIMALS 421 
Letheby (1865) carried out a number of experiments for the purpose of 
studying the effects of nitrobenzene on dogs and cats. The drug was 
invariably administered by introducing it into the stomach. The results 
obtained in his various experiments were fairly similar; therefore the 
following report (page 49 of reference cited), which is quoted verbatim, 
may be taken as characteristic of the results obtained by him: 
Experiment 2.— January 16th, 1862, at half-past three p. m., I gave half a drachm of 
nitro-benzole to a small terrier dog. The poison was poured into the animal’s mouth; it 
caused discomfort, as if from the unpleasant taste, and produced a copious flow of frothy 
saliva. This, however, soon subsided, and for an hour there was no perceptible effect beyond 
a little heaviness of look. At the end of an hour the animal was sick, and after that it became 
sleepy. In another hour it was again sick, and again in a quarter of an hour. For four 
hours the animal lay on its side asleep, and then some water was given to it, which it took 
freely; from that time till midnight nothing appeared to be the matter with it, and the next 
morning it seemed to be quite well, and ate its food heartily. It remained thus all day, 
and was left at night apparently well, but the next morning at half-past six o’clock it was 
found upon its side insensible. The legs were in constant motion, as if the animal was 
running. The head was drawn back, and the muscles of the neck were rigid, as if in spasm; 
the eyes were open, the pupils were widely dilated, and the conjunctiva was insensible to 
the touch. The animal lay in this state for sixty-six hours, that is, nearly three days, and 
then it died as if from exhaustion. During the whole of this time the legs were in constant 
motion; there were occasional spasms, and then a sort of struggle for breath. The heart 
beat in an irregular, tumultuous manner, and the breathing was somewhat laborious. The 
total time which elapsed from the taking of the poison to the death was one hundred and 
four and a half hours. 
The body was opened twelve hours after death. The brain and its membranes were 
very vascular; there was no odour of the poison in any part of the body; the lungs were 
slightly congested; the heart was full of blood on the right side, and there was a little on the 
left; the liver was of a deep purple colour; the gall-bladder was full of bile; the stomach was 
nearly empty, it only contained a little fuid and mucus; there was no sign of irritation. On 
analysis it yielded a trace of aniline, but no nitro-benzole; and nothing was found in the brain. 
Letheby divided the action of nitrobenzene into two classes, character- 
ized respectively by rapidly developing coma and by slow paralysis and 
coma, after a considerable period of inaction. He summarizes the symp- 
toms as follows (page 42 of reference): 
When the effects were speedily fatal, the animals were soon seized with giddiness and an 
inability to walk. The weakness of the limbs first appeared in the hind extremities, and was 
manifested by a difficulty in standing; but very soon it extended to the fore legs, and then 
to the head and neck. There was complete loss of voluntary power; the animals lay upon 
the side with the head drawn a little back, and with the limbs in constant motion, as if in the act 
of trotting or running. The muscles of the back were occasionally fixed in spasm, and every 
now and then the animals had a sort of epileptic fit. They looked distressed, and howled 
as if in pain, and struggled violently; after which they always seemed exhausted, and lay 
powerless. The pupils were widely dilated, the action of the heart was tumultuous and irreg- 
ular, and the breathing was somewhat difficult. For some time, however, the animals 
retained their consciousness, and gave signs of intelligence when spoken to; but suddenly, 
and often at the close of a fit, they became comatose, the eyes remaining open, although the 
conjunctiva was insensible to touch, and the movements of the limbs would nearly cease, 
the breathing became slow and somewhat stertorous, and the animals seemed to be in a 
