174 THERAPEUTICS AND PHARMACOLOGY 



illustration and compare the ferment which is excreted by a bacil- 

 lus or by yeast to the saliva which is said to be poured out by a boa- 

 constrictor over its victim to facilitate its ingestion, while the fer- 

 ments within the microbe may be likened to those in the stomach 

 and intestine of the boa by which it effects the digestion of its prey. 



Other microbes in like manner absorb nutriment and may form 

 and excrete toxins, though both the nutriment and the toxins of 

 bacilli in general differ from those of yeast. 



To recapitulate what I have already said, we see therefore that 



(1) Cells excrete ferments; 



(2) They excrete poisons formed within their bodies; and 



(3) When they are broken up they may liberate other ferments. 



The ferments excreted by microbes apparently prepare the sub- 

 stance in or on which they are growing for assimilation, and the 

 ferments within the cell-body decompose it further in the process of 

 growth. It is probable that all cells, whether they be wandering 

 microbes or cells coordinated in an organism, prepare and assimilate 

 their nutriment by means of ferments, and Macfadyen and I found 

 that not only have bacilli the power of excreting ferments, but 

 apparently they are able to adapt the ferment which they excrete 

 to the soil in which they are growing in much the same way as Paw- 

 low has recently shown that the pancreas in animals modifies the 

 ferments it forms according to the food which it is required to digest. 



Not only is digestion carried on in the stomach and intestines by 

 the ferments which are now so well known even to the general public, 

 pepsin, pancreatin, etc., which dissolve the ingested food so that it is 

 readily absorbed into the circulation and carried to every part of the 

 body, but the other cells which compose the various parts of the body, 

 muscles, nerves, and glands, probably carry on the functions of their 

 life by means of ferments also. By means of these they alter and 

 assimilate the various substances which are brought to them by the 

 blood and juices of the body, and after having supplied their own 

 wants they throw into the circulation the altered residue of their 

 pabulum as well as the substances which they have themselves formed 

 in their processes of growth. They probably repeat in fact what we 

 have already seen to occur with yeast, which not only alters the 

 sugar in which it grows by a ferment which it excretes, but also 

 produces carbonic acid and alcohol by means of a ferment which 

 remains within the yeast-cells so long as these are intact and only 

 becomes liberated when these cells are broken up. 



An excessive quantity of their own products is usually injurious to 

 cells and too much alcohol will stop the growth of yeast. At the same 

 time these products are frequently very nutritious for cells of a differ- 

 ent sort and alcohol furnishes a most suitable pabulum for the organ- 

 isms which produce vinegar. Vinegar in its turn is toxic to the mi- 



