ADAPTATION OF ORGANISMS. 123 



gocytosis in more than one way. The toxic 

 substances may injure the leucocytes to such an 

 extent that they do not readily take up the living 

 organisms; since they represent disintegrated 

 organisms,, they may, like the latter, absorb or 

 "bind" the opsonins of the plasma, on which 

 phagocytosis depends, and thus prevent the action 

 of the opsonins on the bacterial cells; similarly, 

 they bind the bacteriolysins of the serum, and 

 hence divert their action from the living cells; 

 also, since the dissolved organisms are toxic, when 

 the "aggressins" are added to living cultures, the 

 total toxicity for the animal is increased by just 

 that much. There is also evidence to show that the 

 most indifferent proteid substances when injected 

 into an animal may decrease its resistance to infec- 

 tion or intoxication for the moment. Thus Kick- 

 etts and Kirk found that a small quantity of egg 

 albumin, broth, or normal serums (goat, guinea- 

 pig) when injected into white mice, decrease the 

 resistance of the latter to a concomitant inocula- 

 tion with tetanus toxin. The foreign substances 

 were supposed to pre-engage the absorptive and 

 digestive powers of various cells (leucocytes., etc.), 

 so that the toxin was disposed of less readily, and 

 more remained available for the highly susceptible 

 nervous tissues. 



The remarks just made are not intended to cast 

 doubt on the probability that pathogenic micro- 

 organisms produce substances which are antago- 

 nistic to phagocytosis. That the latter action 

 really occurs has already been indicated. 



In previous paragraphs attention was called to Response and 

 the fact that micro-organisms attempt to adapt 

 themselves to their hosts, to the end that the latter 



