40 INFECTION AND RESISTANCE 



jured by the actual growth of the living bacteria. Kruse calls atten- 

 tion to experiments by Burgers in which enormous quantities of 

 cholera poison, i. e., 200 cultures of dead or living cholera bacilli, 

 could be administered to healthy guinea pigs and rabbits by mouth 

 without harm in spite of the fact that these animals are definitely 

 susceptible to the poisons and although the poisons are not injured 

 by the intestinal ferments. It is likely therefore that the absorption 

 of poison begins only after the bacteria have extensively invaded the 

 intestinal mucosa and, by injuring tissue, have opened paths for 

 absorption. In the case of diphtheria probably a similar condition 

 exists in that the localized injury to the mucous membrane at the 

 point of lodgment of the primary infection prepares a portal of 

 entry. The poison of the Bacillus botulinus alone seems to form an 

 exception to this rule, 33 since this substance, though apparently a 

 true bacterial toxin, is absorbed directly from the intestinal canal. 

 With most bacteria this problem does not arise, since the poisons are 

 elaborated within the tissues, where resorption is a necessary result. 

 Like alkaloids and other organic as well as inorganic drugs, the 

 action of many bacterial poisons is largely selective. Most of these 

 poisons may excite inflammatory reactions if concentrated in any 

 part of the body, but, in addition to this, there is a specific distribu- 

 tion after introduction which indicates that the poison goes into 

 selective relationship with certain tissues and cells. This fact is most 

 clearly illustrated by the bacterial hemotoxins which specifically in- 

 jure the red blood cells of the infected individual and by such sub- 

 stances as the leukocidin produced by the Staphylococcus aureus,, a 

 poison which directly and visibly injures the white blood cells. Here 

 the action is specifically aimed at a well-defined variety of body cell. 

 In considering this problem in connection with infectious disease, 

 it is of great importance to distinguish between selective injury by the 

 poisons transported through the body by the lymph, blood, and other 

 channels, on the one hand, and the selective lodgment of the micro- 

 organisms themselves on the other. The latter may occasionally de- 

 pend on local cultural advantages for the particular bacteria in one 

 organ or another, but may just as often be determined by the peculiar 

 manner of entrance to the body which is most suitable for lodgment 

 of the germs in question, and the degree of local resistance at the 

 point of entrance, which determines whether or not the infection shall 

 be locally limited or permitted to invade beyond this point. In the 

 case of a disease like acute anterior poliomyelitis, where our knowl- 

 edge of the microorganisms which cause the disease is yet in its in- 

 fancy, it is impossible to decide whether the injuries noted in the 

 motor areas of the cord and medulla are due to toxins or the lodg- 

 ment of the germs themselves. In the case of rabies it seems reason- 

 ably sure that the microorganisms themselves select the nervous sys- 

 33 Madsen in "Kraus u. Levaditi, etc.," Vol. 1. 



