538 
city milk dealers under ordinary market conditions, were placed in 
the tubes of a small centrifuge and rotated fifteen minutes at the rate 
of 2,000 revolutions per minute. Every sample treated in this way 
deposited a sediment, and microscopic examinations of the sediment 
revealed that 98 per cent contained particles of vegetable matter 
identical in appearance with minute fragments of bovine feces. 
On its face this is a very disgusting condition, but it is unfortu- 
nately even more dangerous than its superficial appearance indicates, 
as the solid impurities that reach the consumer in milk are only a frac- 
tion of the total solid impurities with which it has been in contact. 
Larger masses of feces and other larger, solid impurities that drop 
into milk or are splashed, sprayed, or otherwise introduced into it 
from the environment of cows are removed by the straining to which 
it is subjected before it is poured into the containers in which it is 
sold ; hence only those solid impurities that are small enough to pass 
through the strainer are found when samples of market milk are 
examined. 
What this means relative to the infection of milk with tubercle 
bacilli when it is obtained from or in the environment of tuberculous 
cows is a subject on which it is hardly necessary to enlarge. Xo firm 
union exists between the tubercle bacilli and the feces, throughout the 
entire mass of which they are evenly disseminated. The bacilli are 
present in an easily detached condition; they are probably washed 
free from the feces that finds its way into milk, and they are too small 
to be removed by the strainer. In a test made regarding this matter 
it was found when guinea pigs were inoculated with normal, fresh 
milk to which small amounts of fresh feces from tuberculous cows had 
been added, amounts no greater than commonly fall into the milk pail 
during ordinary milking, that those inoculated after the milk had 
been strained succumbed to tuberculosis as rapidly as those inoculated 
with the milk before it was strained. 
That the solid material found in milk as sediment can not be taken 
as a true measure of the amount of solid, foreign, contaminating 
material with which it has actually been in contact is shown by the 
following observation. Among the samples of milk examined rela- 
tive to fecal content a number were found, with little or no vegetable 
sediment, that yielded cream in the tubes of a centrifuge discolored 
precisely like the cream obtained from milk to which uncommonly 
large quantities of cow feces were intentionally added. Such milk, 
because of its freedom from sediment and its discolored cream, must 
be regarded as very dirty and very dangerous milk that has been 
exceptionally well strained. 
The specific gravity of tubercle bacilli is higher than that of milk, 
and hence it does not seem unreasonable to suppose that they can be 
removed from it by sedimentation. This supposition would be true 
