666 THE INTERNAL SECRETIONS AND IMMUNITY. 



cies susceptible to such a reaction that may either be physio- 

 logically formed in the organism or enter the blood-stream 

 from without, is the reagent to which all such processes are due 

 has likewise been demonstrated by its role in general functions: 

 the combustion of sugars and other hydrocarbons, the elabora- 

 tion of uric acid, phosphoric acid, etc. 



That the thyroid secretion, which contains iodine in organic 

 combination, as demonstrated by various investigators, sustains 

 the functional activity of the anterior pituitary body and, 

 therefore, of the entire adrenal system. Being endowed with an- 

 tiseptic and stimulating attributes, owing to the presence of io- 

 dine, it may also act as such in the blood while in transit, but, as 

 no experimental proof to this effect is available, its action upon 

 the anterior pituitary body can alone be taken into account. 



In view of all these facts it seems evident that phagocytes, 

 alexins, trypsin, and the oxidizing substance are the four main 

 defensive agencies with which the organism is provided to 

 antagonize pathogenic germs, their toxins, and other organic 

 poisons; and that they represent the active constituents of 

 antitoxin. We can therefore conclude, for the time being, that: 



Antitoxin, the antitoxic serum obtained from animals by 

 means of injections of diphtheria toxins, is composed of the fol- 

 lowing main bodies: (1) Blood-serum, which acts as vehicle. (2) 

 Alexins, which act as bactericidal agents. (3) Trypsin, which acts 

 as toxin-, toxalbumin- (including vegetable poisons), and venom- 

 reducing agent. (4) Oxidizing substance, which submits to oxida- 

 tion all toxics possessed of sufficient affinity for oxygen. 



A number of questions are awakened by this list, however. 

 How do the alexins originate, and to what agency do they owe 

 their bactericidal properties? Again, considerable evidence, 

 clinical and experimental, has shown that the protective func- 

 tions of the organism fluctuate under certain conditions. The 

 introduction of salt solution into the blood-stream, for instance, 

 often causes a seemingly moribund case to at once enter the 

 stage of convalescence. This suggests that we have only studied 

 the grosser phases of the immunizing process so far, and that 

 our inquiry must include, if it is to be of some practical value, 

 an analysis of the physiology of immunity, and of the intrinsic 

 conditions that tend to antagonize the immunizing process. 



