84 Infection 



Fever and suppuration are, therefore, non-specific actions, be- 

 cause numerous micro-organisms share in common the qualities 

 productive of these conditions. 



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 sweUing 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 effect of the activity of the various products of any micro- 

 organism produces a typical effect, differing from the total effect 

 of the operation of other micro-organisms, and a recognized type 

 of disease results, it becomes possible to say that the micro-organism 

 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 profoundly impressed by it, and definite responses 

 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 the cells 

 of the nervous system to which it is secondarily carried by the 

 blood. 



SPECIFIC AFFINITY OF THE CELLS FOR THE TOXINS 



The cells of the connective tissue in which the tetanus bacillus 

 is Hving show Httle reaction, but the motor cells of the central 

 nervous system, having a greater affinity for it, are profoundly 

 impressed, so that convulsions 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 have 

 specific reactions, the cells of the respiratory centers seeming to 

 be most profoundly affected by them. 



The diphtheria bacillus, when observed in ordinary throat in- 

 fections, is seen to produce a pseudomembranous angina which 

 results in part from an irritative local action of the organism, which 

 it shares in common with many others, and in part from some 

 coagulating product which it shares in common with a few— pneu- 

 mococcus, streptococcus, etc. Neither of these reactions is specific, 



