250 SUSCEPTIBILITY AND IMMUNITY. 
remove progressively all the material necessary for the development of ‘the 
parasite.” 
In discussing this theory, in a paper published in the American 
Journal of the Medical Sciences (April, 1881), the writer says: 
‘Let us see where this hypothesis leads us. In the first place, we must 
have a material of small-pox, and a material of measles, and a material of 
scarlet fever, etc., etc. Then we must admit that each of these different 
materials has been formed in the system and stored up for these emergencies 
—attacks of the diseases in question—for we can scarcely conceive that they 
were all packed away in the germ cell of the mother and the sperm cell of 
the father of each susceptible individual. If, then, these peculiar materials 
have been formed and stored up during the development of the individual, 
how are we to account for the fact that no new production takes place after 
an attack of any one of the diseases in question ? 
‘‘ Again, how shall we account for the fact that the amount of material 
which would nourish the small-pox germ, to the extent of producing a case 
of confluent small-pox, may be exhausted by the action of the attenuated 
virus«(germ) introduced by vaccination? Pasteur’s comparison of a fowl 
protected by inoculation with the microbe of fowl cholera, with a culture 
fluid in which the growth of a particular organism has exhausted the pabu- 
lum necessary for the development of additional organisms of the same kind, 
does not seem to me to be a just one, as in the latter case we have a limited 
supply: of nutriment, while in the former we have new supplies constantly 
provided of the material—food—from which the whole body, including the 
hypothetical substance essential to the development of the disease germ, was 
built up prior to the attack. Besides this we have a constant provision for 
the elimination of effete and useless products. 
‘This hypothesis, then, requires the formation in the human body, and 
the retention up to a certain time, of a variety of materials which, so far as 
we can see, serve no purpose except to nau the germs of various specific 
diseases, and which, having served this purpose, are not again formed in the 
same system, subjected to similar external conditions, and supplied with the 
same kind of nutriment.” 
It is unnecessary to discuss this hypothesis any further, inasmuch 
as it is no longer sustained by Pasteur or his pupils, and is evidently 
untenable. 
The Retention Theory, proposed by Chauveau (1880), is subject to 
similar objections. According to this view, certain products formed 
during the development of a pathogenic microérganism in the body 
of a susceptible animal accumulate during the attack and are subse- 
quently retained, and, being prejudicial to the growth of the particu- 
lar microédrganism which produced them, a second infection cannot 
occur. Support for this theory has been found by its advocates in 
the fact that various processes of fermentation are arrested after a 
time by the formation of substances which restrain the development 
of the microérganisms to which they are due. But in the case of a 
living animal the conditions are very different, and it is hard to con- 
ceive that adventitious products of this kind could be retained for 
years, when in the normal processes of nutrition and excretion the 
tissues and fluids of the body are constantly undergoing change. 
Certainly the substances which arrest ordinary processes of fermen- 
