CONTRIBUTION TO THE STUDY OF SERUM-THERAPY IN DIPHTHERIA. 669 
branes become detached and disappear, when these guinea-pigs 
are compared with control ones that die with extensive lesions 
of the vagina in five to six days. 
3. Action of the serum on animals whose tracheas are in - 
oculated .—Tracheal and laryngeal diphtheria is, in children, by 
far the most severe form. The bacillus often invades the lung, 
when the absorbing surface becomes enormous and the poison¬ 
ing is very rapid. Besides, the respiratory difficulty may call 
for tracheotomy, in which the wound itself facilitates secondary 
pulmonary infection and increases the danger. 
In order to properly judge what results we might obtain in 
actual practice, it was therefore necessary to experiment with 
animals whose trachea or larynx were involved. 
Rabbits are best for this purpose. The trachea is incised, 
the mucous membrane scratched with a platinum needle and 
then inoculated with the needle charged with diphtheritic bacilli. 
The wound is then closed. On the morrow these animals have 
fever, in 48 hours the breathing is uneasy and noisy, as the 
false membianes keep developing ; one can even perceive, at a 
distanced, a very characteristic noise. 
Guinea-pigs so inoculated commonly die in three days when 
not treated. Rabbits die in from three to five days. In these 
animals the trachea and the larynx were injected and false 
membranes coveied the mucous surfaces and often extended to 
the first ramifications of the bronchi. The lungs, congested in 
spots, showed a few bacilli. 
When guinea-pigs or rabbits are thus inoculated, after hav¬ 
ing received an injection or preventive serum, they do not 
acquire diphtheria, or, at any rate, they show no manifestations 
of it. When the amount of serum is insufficient the disease 
stops for a time, and then there is a relapse. In some instances, 
after too small an injection, we have seen guinea-pigs go 
through a mild diphtheria and die two months later with lesions 
of the kidneys and the suprarenal capsules. 
If the serum is injected after inoculation there is an arrest 
of the evolution of the diphtheria. 
