MECHANISM OF INFECTION AND IMMUNITY 235 



secretions elaborated by the body cells. It is a phenomenon of the 

 disposal of foreign and harmful material and it must be recognized 

 as beneficent. However, there is a point above which it becomes a 

 danger per se. In parenteral digestion, the following sources of heat 

 production must be evident: 1. The unaccustomed stimulation and 

 consequent increased activity of the cells which supply the enzyme 

 must be the source of no inconsiderable increase in heat production. 



2. The cleavage of the foreign protein increases the heat liberation. 



3. The reaction between the digestive products and the tissues leads 

 to increased heat production. I regard the first and third as the 

 important sources of the overproduction of heat in the infectious 

 diseases. 



There are many conditions affecting the course of a fever and 

 some of these may be mentioned. Some viruses sensitize more quickly 

 and thoroughly than others. It is possible that the living bacterial 

 cells, so long as they are living, do not sensitize. Some of the bacterial 

 protein must pass into solution before cell penetration, which seems 

 essential to thorough sensitization, can occur. A living colon bacillus 

 of not more than twenty-four hours' growth, when injected intra- 

 abdominally in a guinea-pig, requires about ten hours to sensitize. 

 With dead bacilli the time is reduced to half, while with old autolyzed 

 cultures, in which the sensitizing group is already in solution, the time 

 is further shortened. Some pathogenic bacteria, like the tubercle 

 bacillus, have been so long parasitic that they have learned to protect 

 themselves by deposits of fats and waxes. Others form capsules which 

 serve a like purpose. In this way they are probably protected to some 

 extent against the destructive enzymes elaborated by the body cells. 

 In all the infectious diseases, the destruction of the invading organism 

 is modified and delayed by the altered relation between ferments and 

 substrate and the accumulation of fermentative products. The blood 

 is a highly active digestive fluid with a finely adjusted balance between 

 ferment and anti ferment, which will soon be better understood and 

 the solution of this problem will add another triumph to scientific 

 medicine. When the ferment in the blood is suddenly activated, 

 immediate death results, as is seen in anaphylactic shock. When 

 properly regulated, this delicate mechanism protects against harmful 

 bodies, both those introduced from without and those generated within. 



