TETANUS. 
389 
The period of incubation seems to be extremely variable 
in both man and animal; in some cases existing only twenty- 
four hours, in others lasting weeks between the time of infec¬ 
tion and the first manifestations of the disease. This may be 
accounted for. First, the number of bacilli introduced into 
the system may be so small that a longer time is necessary 
before the disease is manifest. Second, the character and 
location of a surgical operation in many instances acts as an 
infection atrium, also the anatomical characteristics of the tis¬ 
sues surrounding it may influence the time which is necessary 
to develop the disease. 
The investigations of Brieger have shown that tetanic 
convulsions in animals are produced by injections of tetanin, 
one of the toxic ptomaines derived from cultures of the bacil¬ 
lus of tetanus. It is more than probable that the active symp¬ 
toms of tetanus are due, not to the presence in the tissues of 
the bacillus, but to the toxic action of the ptomaines on the 
spinal cord; so that the duration of the period of incubation 
is further modified by the capacity of the infected tissues to 
yield to different ptomaines. As in the second instance the 
character of certain surgical operations play an important 
part as an infection-atrium in the practice of veterinary sur¬ 
gery. My experience leads me to believe that operations 
and injuries in the soles of the feet, and as a signal to castra¬ 
tion and the extirpation of the thyroid gland for bronchocele 
are operations in which the greatest tendency to this disease 
resides. Weiss reported thirteen cases of tetanus occurring 
after removal of the thyroid gland. In fifty-three total extir¬ 
pations of the thyroid gland for goitre made by Billroth 
tetanus followed in twelve cases, while no cases occurred in 
one hundred and nine partial operations. Gautier has col¬ 
lected seventy-four cases of tetanus, thirty-six following 
abortion and thirty-eight following confinement. Autopsies 
were made in fifteen cases. Three presented on microscopical 
examination of the brain and cord no appreciable lesion ; in 
one case a retained putrefied placenta was found in the 
uterus ; in five suppurative metritis ; in one, ovarian cyst; in 
one, hemorrhage into the lateral ventricles. Ten patients 
recovered, five after abortion, five after labor. 
