603 
It seems that the nearer the various varieties of dysentery and 
typhoid bacilli approach the colon bacillus the less virulent they 
become. 
The dysentery bacillus has only been known since 1898 and its rela- 
tion to milk is not well worked out, but there can be little doubt that 
it is a means of spreading the disease. 
The Bacillus proteus or proteus vulgaris. — This is a common organ- 
ism found frequently in normal feces in moderate numbers and com- 
monly contaminates milk. This bacillus produces the tryptic fer- 
ment that peptonizes casein and it also attacks carbohydrates. That 
this organism may induce acute diseases of the gastrointestinal tract 
appears to be well established. 
The tubercle bacillus. — Tubercle bacilli have frequently been found 
in milk and their relation to disease is discussed elsewhere. 
Kochi s cholera bacillus — 1 The specific cause of cholera requires an 
alkaline medium in which to grow. As milk is usually acid or soon 
becomes acid the cholera vibrio has little chance of survival, though 
small outbreaks of cholera have been traced to milk. 
The Micrococcus melitensis. — This organism causes Malta fever 
and is found in goats’ milk. It is fully discussed elsewhere in this 
bulletin. 
The Bacillus diphtherias. — The diphtheria bacillus finds favorable 
conditions for growth and multiplication in milk. A number of out- 
breaks of diphtheria have been traced to milk so contaminated. 
Streptococci and Staphylococci. — These form an exceedingly 
important group of organisms on account of their frequent and 
exceptional virulence. They are ahnost constantly found in milk, 
frequently in great numbers. Herter says that the human intestinal 
tract under normal conditions is probably most of the time free from 
pathogenic varieties of this group of cocci. 
In healthy adults these pathogenic bacteria introduced with milk 
are ordinarily quickly destroyed in the upper portion of the tract. 
During infancy the digestive tract is very much less resistant to 
streptococcic infection. An invasion of the mucous membrane by 
streptococci is of frequent occurrence and may be associated with 
disturbances of almost any grade of severity. 
It has been shown by Bucher in this country, and by Escherich of 
Germany, that some of the severest forms of infantile ileo-colitis are 
associated with streptococcic infections and are probably dependent 
upon them. 
The Streptococcus lactis , first described by Kruse, has been proved 
by Heinemann in this country to be one of the common causes of 
lactic acid fermentation in milk. It appears to be indistinguishable 
from the pathogenic forms and is always present in market milk. 
