436 
Some Relations of Biology to Agriculture. 
there must be susceptibility in certain cells of the body ; secondly, 
the inciting cause is the specific micro-organism. Indeed, it might 
be said that the primary cause lies in the tissue itself. Then there 
is the ever-interesting subject of immunity against disease secured 
by the use of sterilised culture of the various specific micro-organ- 
isms. Is such immunity, which has already been obtained in a 
number of diseases, due to a true vaccination, or is it simply due to 
the establishment of a tolerance for a poison ? How long will the 
immunity thus secured continue ? 
The study of food and drink by the bacteriologist has only begun. 
In many of the infectious diseases the specific poison finds its way 
into the body through the mouth. The chief source of infection 
with cholei'a in India is the drinking-water, which is collected 
during the rainy season in tanks that not only serve the inhabitants 
for water-supply, but are also used as laundry and bath tubs. And, 
in the western world, many towns discharge their sewage into bodies 
of water from which they or other communities derive their supply 
for drinking purposes. The risk of seriously affecting the health, 
by eating food which has partially undergone putrefactive changes, 
increases every year with the growing consumption of canned and 
otherwise preserved food. 
fei-'j Every important scientific discovery sooner or later finds its 
practical application. What could have been more unpromising of 
practical results than the discovery by Pollemler, in lSi9, of micro- 
organisms in the blood of an animal sick with anthrax ? When 
this observer reported that he had seen minute forms of life 
in the blood, some said that the objects were bits of fibrin, others 
that they were not real at all but due to defects in the glass, while 
still others hinted very strongly that the defects really existed in the 
observer's brain ; but truth prevailed, and from that observation, or 
discovery, as a starting-point, the science of Bacteriology has been 
developed to its present importance, and, by virtue of the facts under- 
lying this science, the spread of infectious diseases has been checked 
in a manner that would never have been thought of in the past. lb 
was owing to knowledge, founded upon the discovery under notice, 
that Asiatic cholera was arrested in New York harbour in 1888, 
and prevented from spreading through the United Stsites and 
Canada. -yy -pj^Exk 
