BACTERIA IN INFECTIOUS DISEASES. 247 



which the growth of a particular organism has exhausted 

 the pabulum 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 nourish the germs of various spe- 

 cific diseases, and which, having served this purpose, are 

 not again formed in the same system, subjected to simi- 

 lar external conditions, and sup plied with the same kind 

 of nutriment. 



"The difficulties into which this hypothesis leads 

 certainly justify us in looking further for an explanation 

 of the phenomenon in question. This explanation is, I 

 believe, to be found in the peculiar properties of the 

 protoplasm, which is the essential frame-work of every 

 living organism. The properties referred to are : the 

 tolerance which living protoplasm may acquire to cer- 

 tain agents which, in the first instance, have an inju- 

 rious or even fatal influence upon its vital activity, and 

 the property which it possesses of transmitting its pecu- 

 liar qualities, inherent or acquired, through numerous 

 generations, to its offshoots or progeny. 



" Protoplasm is the essential living portion of the cel- 

 lular elements of animal and vegetable tissues ; but as 

 our microscopical analysis of the tissues has not gone 

 beyond the cells of which they are composed, and is not 



