349 
purity, for the liquid as it issues is exposed to contamination 
both from the hands of the milker and from the surface of 
the test itself. It is not therefore surprising that the results 
of our experiments with this secretion were not uniform. 
Their variations, however, exhibit so complete a correspond- 
ence with the varying conditions of the experiments, that 
they are scarcely less confirmatory of the general conclusions 
we have arrived at than if they had been positive. 
February 28.—Milk was received directly from the cow 
into two flasks (marked a and 4) which had been previously 
superheated. The flasks were immediately plugged with 
cotton wool. Another specimen of milk ‘‘as delivered to 
customers,” was brought from the dairy at the same time 
in a clean bottle which had not been superheated. All the 
specimens were alkaline. On March 4 it was found that the 
milk in the bottle was slightly acid and crowded with bacteria. 
On the 9th it was curdled and smelt offensively. The flask 
a was also acid on March 4, and contained a few groups of 
bacteria. In the flask 4 the acid reaction was scarcely appre- 
ciable, and no bacteria could be discovered in it. On the 9th 
the contrast between a and 0 was still very striking, the 
liquid in @ having separated into whey and curd, while 6 
remained apparently homogeneous. Charged eprouvettes 
were then impregnated with drops of the liquid in 6 in 
which no bacteria could be detected. After a few days 
bacteria appeared in the test liquid, and in the liquid which 
still remained in the flask. 
The difference between a and } was of course accidental, 
for both were exposed to equal chances of impregnation. 
XXVI.—February 21.—It has been already stated that 
superheated tubes containing egg albumen which had been 
kept from August, 1870 to March, 1871, were found abso- 
lutely free from organisms, and to all appearance unaltered. 
The liquid contained in one of these tubes which was per- 
fectly limpid was emptied into a superheated eprouvette and 
impregnated with two drops of cold distilled water. On 
March 2 the liquid had acquired a yellowish green tint, a 
scum had formed on its surface, and the liquid was full of 
separate bacteria. 
XXVII.—March 20.—Pus was collected from a deep- 
seated abscess in the thigh of a child by introducing the 
capillary end of a collecting tube into the path of the 
bistoury which had been used for opening it, the bistoury 
having been itself immersed in boiling water. It was then 
transferred to a small eprouvette and exposed to the air. On 
March 30 there were no bacteria. It was then diluted with 
