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live only so long as the air to which the liquid is exposed 
still contains sufficient oxygen. If microzymes exist in great 
numbers in a liquid, air which has remained for a length 
of time in contact with it has a large excess of carbonic acid, 
and occupies less volume than it did originally under the 
same conditions of pressure and temperature. We have 
found that in such air a taper is immediately extinguished, 
whence it would seem that microzymes are able to use up 
nearly the whole of the oxygen which is supplied to them. 
When microzymes grow at the expense of disintegrating 
organic substance, it cannot be supposed that they avail 
themselves of the albuminates already existing in it to build 
up the material of their own bodies. If this were the case 
it would be impossible to understand the fact that they grow 
quite as luxuriantly when the nitrogen they require is sup- 
plied to them in the form of salts of ammonia, as when it is 
in the form of ready-made albumen; for clearly it must re- 
quire a much greater expenditure of plastic energy to build 
up protoplasm of elements derived from such sources, than 
merely to convert one albuminous compound into another. 
It therefore seems probable that bacteria do not use the 
material on which they feed until it has already been con- 
verted by oxidation or by splitting into lower chemical 
combinations. 
The question how far microzymes are the cause of putre- 
faction will, I think, be elucidated by the results of the fol- 
lowing experiments. It will be shown that so long as the 
germinal matter of microzymes is excluded, animal fluids or 
tissues withstand decomposition for very long periods, while 
the slightest contact with media containing this material at 
once determines septic changes. Consequently it can be 
asserted positively that under certain circumstances the 
presence of microzymes excites putrefaction; but the facts 
do not afford grounds for stating that they are the cause of 
putrefaction, or that if it were not for them the process would 
be postponed indefinitely. It is indeed asserted by chemists, 
and we do not propose to deny, that organic matter may, 
under the influence of heat and moisture alone, undergo 
decompositions which present all the chemical characters of 
putrefaction, even though no microzymes be present. 
Method —As regards the questions which form the prin- 
cipal subject of this report, we at present possess no exact 
information. As has been already stated, there is a general 
belief that microzymes exist potentially in the air, and it is 
also admitted that they may be met with in the blood in 
certain septic diseases. MHallier, on the other hand, finds 
