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D. E. SALMON. 
endue and recover from the effects of the poison excreted by the 
microbes, but it must also explain why the multiplication of these 
micro-organisms ceases and becomes impossible even in the liquids 
of the body, and where they are uot in actual contact with the 
cells. The tissues are, as we know, penetrated by channels some 
of which contain blood and others lymph, and there are every¬ 
where spaces between the cells filled witli a nutritive liquid which 
sustains the life of these minute constituents of the body. These 
chaunels and spaces, compared with the size of the microbes, are 
simply enormous, and, without the part of my theory relating to 
the oxygen supply, we can no more understand how the cells (in 
their walls) can prevent the multiplication of the microbes in the 
liquids flowing between them than we can conceive of the trees 
on a river’s bank preventing the multiplication of the fish in its 
waters. There are only two conceivable explanations of the phe¬ 
nomenon ; one is, that the cells excrete something injurious 
to the microbes, and the other is, that the cells withdraw some¬ 
thing essential to the microbe’s growth. The former is unten¬ 
able, because the liquids which are unsuitable to the microbe’s 
growth when within the body of the insusceptible animal become 
very favorable for its growth when removed from the influence 
of the living protoplasm. Evidently, then, they do not contain 
any injurious principle. Turning to the other explanation, we 
must admit for the same reason that whatever is abstracted by 
the cells must be something that can be supplied by contact with 
the atmosphere. Now, is there any other element than oxygen 
which can be supplied by the atmosphere and at the same time 
is so essential to the multiplication of the microbes? 
From the facts I have mentioned, and from many others 
which I have neither the time nor the space to enumerate, it has 
seemed to me that when the cells are exercising their functions 
in a normal manner, they have such an affinity for oxygen that 
this gas is completely removed from the liquids in the interior of 
the body; and, consequently, microbes which require oxygen can 
multiply only when sufficient poison is introduced witli them, or 
when they are present in sufficient number to produce enough 
poison to depress the activity of tiie cells and prevent them from 
so completely taking up the oxygen. This theory may be wrong, 
