DR. WILLEMS. 
357 
But, in admitting that pleuro-pneumonia is contagious, could 
it not originate spontaneously from internal causes, or has it always 
necessarily as an originating cause the impregnation of the organ¬ 
ism by a virus from the outside ? 
This last opinion is the most accredited and the best founded. 
“ Can contagious peripneumonia,” said M. Henry Bouley, 
“ originate spontaneously ? ” 
“No,” says he, “ for it is contagious ,”—M. Tabourin answers us. 
“As long as the question of its contagiosity remained doubtful, its 
spontaneous developement might be admitted as probable; but 
since the researches of Dr Willems upon the contagion and the 
virulency of this species of peripneumonia, M. Tabourin cannot 
comprehend that its spontaneity could still count partisans. 
Starting from the absolute principle that contagion is identical 
with generation, he is necessarily brought to deny the possibility of 
the spontaneous development of a disease whose contagious prop¬ 
erties are known. This manner of conclusion is consequent with 
the doctrine, but is it concordant with facts ? ” 
In 1874, Mr. Bouley seemed to be still in doubt, but I be¬ 
lieve that at present his conviction is in favor of the solution of 
that question. 
My personal experience, after a close observation during long 
years, of the march of pleuro-pneumonia, has convinced me that 
this affection is exclusively contagious, transmissible from sick to 
healthy animals by inoculation and by infection, that is to say arti¬ 
ficially by tixed and naturally by volatile virus. It never origina¬ 
ted spontaneously. 
Mr. Pasteur does not admit the spontaneity for transmissable 
diseases, and certainly lie is right for what concerns the etiology 
of several contagious diseases, whose parasitic nature is already 
known. This principle is also applicable to peripneumonia, whose 
special factor is a parasite, a living being. 
Gentlemen, I will try to demonstrate to you that facts 
based, I repeat, upon rigorous observation and experimenta¬ 
tion. justify this opinion. The solution of the question of 
the spontaneity of pleuro-pneumonia is, nevertheless, of 
great importance in practice, as upon it depends the adminis- 
