De Zouche. — Bacteria and tliclr Belation to Disease. 43 



have been known from the earhest times — that is, by their pro- 

 ducts — but the discovery of the vegetable nature of ferments 

 began with that of the yeast-fungus by Cagnard de la Tour in 

 1828. It was reserved for M. Pasteur to show the exact rela- 

 tion of the bacterial ferments to then- specific fermentations. 

 While the term " ferment " is very commonly applied to the 

 bacteria, or vegetable organisms causing the fermentation, it is 

 now used by many to indicate a substance secreted by the 

 bacteria which is the real ferment or enzyme. This substance 

 may be separated from the bacteria producing it, and cause 

 fermentation, or the bacteria may be destroyed while the fer- 

 ment remains active. 



The mode in which the enzyme, or ferment, acts is by the 

 formation of leucomaines in the body, or ptomaines in de- 

 composing animal substances. Our knowledge of these bodies 

 being comparatively recent, I may be permitted to explain 

 that ptomaines are basic bodies resembling alkaloids, de- 

 veloped in decaying animal matters. It may perhaps be right 

 to call them alkaloids. The alkaloids resulting from the de- 

 composition of albumen in the living body are called leuco- 

 maines. The poisoning caused by tamted fish, or by " high" 

 meat, is due to ptomaines, and the cramps and spasms of 

 cholera are believed to be caused by the ptomaines — or, perhaps 

 rather, leucomaines — formed by the comma-bacillus in the 

 intestines. Many of the ptomaines and leucomaines are 

 intensely poisonous. 



Epidemiology. 



The discovery of bacteria as the cause of disease will 

 doubtless in time elucidate many of the difficulties connected 

 with epidemiology, and perbaj)s enable us to account for the 

 rapid spreading of an epidemic fever, or its appearance in 

 places far away from the presumed source of infection, or for 

 its spontaneous disappearance. There is, jDerhaps, no question 

 in connection with the infective fevers of greater interest or 

 importance than that of their mode of spreading as epidemics. 

 The occurrence of cholera in India, for instance, is justly re- 

 garded with alarm throughout Europe and x\merica, for with 

 the constant travel and commerce the bacillus is sure to find 

 its way westward and northward. Hitherto the knowledge 

 we have had of epidemics has been chiefly confined to the his- 

 tory of their outbreak and of their line of march, and of the 

 fatalities occasioned by them, while as to the occurrence of 

 sporadic cases of disease we were thrown back on the theory 

 of generation de novo. Influenza, for instance, epidemics of 

 which have been recorded from the year 1173 up to the pre- 

 sent time, and which are tabulated in the learned work of 

 Hirsch, is found to travel from east to Nvest, sometimes spread- 



