CHEMICAL CEPTORS 107 



and loss of appetite which inaugurate typhoid, we have 

 a picture of the long, slow course of the disease which 

 involves the digestive apparatus and exhausts the 

 system. In the thickened voice, the difficult breath- 

 ing and the abrupt high rise in temperature in diph- 

 theria, in the activated alee nasi, the rapid respiration 

 and the high fever of pneumonia, we have brief sum- 

 maries of the quick and desperate combats with infec- 

 tion which are waged between host and invader before 

 victory is declared for one or the other. 



Undoubtedly, each move in these fast and furious 

 struggles, or slow sieges, between man and his micro- 

 scopic enemies is typical of the long and strenuous bio- 

 logic contest which has gone on for ages between the 

 two adapting organisms the host and the invader 

 umpired impartially by natural selection. It is rea- 

 sonable to believe that every advance of the human 

 organism toward immunity has been met by a like 

 advance on the part of the microorganism toward 

 a more effectual attack and resistance. This is evi- 

 denced by the increased vitality of certain specific 

 microorganisms which survive a curative dose of 

 mercury or arsenic in the system. It was noticed by 

 Ehrlich that a large initial dose of the specific drug is 

 of more value in destroying the spirochetae than a series 

 of minor injections, which are lessened in efficiency 

 by reason of the fact that portions of the culture which 

 survive the first dose become adapted to withstand a 

 larger dose. The desperate struggle of the organism 

 in acute infection bears testimony to the fact that the 

 rules of fight for these encounters have been firmly 

 established and standardized. Man and the acute 



