72 Infection 



The primary irritation is therefore a quality which many 

 bacteria share in common, but the secondary suppuration, 

 one peculiar to a few. 



Irritation and suppuration are therefore non-specific 

 actions, because numerous micro-organisms share the quali- 

 ties productive of these conditions in common. 



If the bacteria are rapidly invasive, but still have injurious 

 products of the intracellular variety, they are apt to share 

 certain qualities, such as the swelling of the lymph nodes, 

 etc., in common, so that such lesions cannot be considered as 

 specific. So soon as any one of the products is discovered to 

 give some single lesion peculiar to that organism by which 

 it is produced, or so soon as the total results of the activity 

 of the various products of any micro-organism produce a 

 typical result, differing from the total results of the operation 

 of other micro-organisms, so that a recognized type of dis- 

 ease results, it becomes possible to say that the micro-organ- 

 ism in question is specific. 



The most striking examples of the specific action of 

 bacterio- toxins is, however, seen in those cases where soluble 

 extracellular metabolic products of bacterial energy are 

 liberated into the body juices so as to be conveyed by the 

 circulatory system to all parts of the body. Those cells 

 most susceptible to its action are then first or most pro- 

 foundly impressed by it, and distinct physiological activities 

 brought about. Thus, the soluble toxin of tetanus causes no 

 visible reaction in the cells with which it first comes into 

 contact at the seat of primary infection, because these cells 

 are either less susceptible to its influence, or are less well 

 able to show its effects, than remote cells of the nervous 

 system to which it is secondarily carried by the blood. 

 The cells of the connective tissue in which the tetanus bacillus 

 is living show little reaction, but the motor cells of the 

 central nervous system are profoundly impressed, and con- 

 vulsions of the controlled muscular system are brought 

 about. This special excitation of the nerve cells is specific 

 because no other bacterio-toxin is known to produce it and 

 it is attributed to special selective affinities of the nerve cells 

 for the poison. This affinity has its analogue among the 

 poisons of higher plants, thus, strychnin has a similar 

 selective affinity and is also said to be specific in action upon 

 the motor cells. 



The venoms of various serpents, especially the cobra, also 



