PART I. 
INTRODUCTOHY 
In view of the fact that 
3 cause of typhoid fever appears to be able to survive for I 
the environment of man, it becomes important to di.scovc 
behavior under various natural conditions. Some knowled-.- m, .m,s 
monly confiidcred to lie 
arly as niaj 
kind wc I 
already in the case of heat and light; some, also, in respect to low tompcr.'.ti.re.s 
under certain conditions. But a careful review of the present state of our knowl- 
edge in regard to the influence of cold upon the bacillus of typhoid fever shuws th.-.t 
much still remains to be done in order to make our knowledge in this direction 
more precise. 
The subject assumes great practical importance when we begin to consider the 
influence of external conditions upon the longevity of the bacillus in nature, par- 
ticularly in those regions in which there is a considerable variation of climate. It 
was a theory formerly widely held that the specific organism of typhoid fever was not 
only capable of enduring for a long time outside the human body, but even tli;it a 
residence in earth, filth heaps, and the like was an essential phase in its life hi-s- 
tory. Modern researches have thrown grave doubt upon this earlier theory, but at 
the same time rigid inquiry into epidemics and further knowledge of the disease itself 
nave shown how readily the micro-organism may become widely distributed in the 
environment. Prolonged and careful studies of the influence of temperature upon 
the bacillus of typhoid fever, have led us to believe that this factor plays a part in 
the seasonal distribution of the disease which is of the highest importance, making it 
possible to explain, by the co-operation of this and other factors, such as light and 
ui'yness, certain phenomena hitherto inexplicable or little understood. An obvious 
and direct application of the principles worked out concerns one of the principal food 
supplies of man, and an important section of the following paper is therefore devoted 
to a consideration of the danger of the conveyance of the disease in question by pol- 
luted ice. 
