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contamination, and so to obtain a positive answer to the ques- 
tion; but this does not render it the less advantageous to 
compare the varying effects of contamination with the con- 
ditions to which they correspond, for by so doing we acquire 
a better knowledge of the nature of these causes, and of the 
means of obviating them. 
The experimental results are stated under three headings, 
according as they relate to the conditions which limit the 
evolution of organic forms, and particularly microzymes, in 
test liquids; to their distribution in ordinary water and in 
most substances; and lastly to their occurrence in the tissues 
and liquids of the animal body. 
While considering myself exclusively answerable for the 
accuracy of every statement contained in the report, I am 
anxious that in so far as the investigation has been a suc- 
cessful one, my assistant, Dr. Ferrier, by whom many of the 
experiments were both planned and carried out, should 
participate in whatever credit may be accorded to me. 
Section 1.—Hzperimental Determination of the Conditions 
which govern the Development of Microzymes in certain 
Organic Liquids to be used as Tests. 
I—July 22nd, 1870.—A large number of capillary tubes 
prepared for the purpose were filled with serum of blood 
obtained from a guinea pig a few hours before. According 
to the mode of filling, and the conditions under which they 
were subsequently placed, the tubes were divided into five 
batches, designated respectively a, b, c,d, and e. The tubes 
@ were exposed, unsealed, to the air of the laboratory; 6 
were hermetically sealed ; c were sealed, and thereafter placed 
in the incubator, in which a temperature of about 40° C. was 
maintained during the whole period of the investigation, with 
the aid of a Geissler’s regulator; d were sealed and heated 
in the oven to 180° C., and thereafter exposed to the air of 
the laboratory by breaking off one end; e were sealed and 
heated in the same manner as d, and then placed in the in- 
cubator. The tubes were examined at various periods within 
a month after they were prepared. Bacteria were found in 
numbers in a, b, and c, but no organic forms could be detected 
indande. The remainder of these two batches were there- 
fore preserved for further examination, until the beginning 
of March, 1871. They then exhibited the appearances always 
observed under the microscope in superheated serous liquids,} 
1 The most remarkable peculiarity of such liquids is that they contain 
