DEFENSIVE FACTORS OF THE ANIMAL ORGANISM 249 



Thus, in epidemic meningitis, such sera have proved extremely useful 

 in the hands of Flexner, when injected directly into the spinal canal. 



ANTIBODIES AND THE SUBSTANCES GIVING RISE TO THEM 



In the foregoing sections we have seen that the process of active 

 immunization so changes the animal body that it becomes highly 

 resistant against an infection to which it had formerly in many in- 

 stances been delicately susceptible. In the absence of visible anatomical 

 or histological changes accompanying the acquisition of this new power, 

 investigators, in order to account for it, were led to examine the 

 physiological properties of the body cells and fluids of immunized 

 subjects. While it was reasonable to suppose that all the cells and 

 tissues were affected by, or might have taken part in, a physiological 

 change so profoundly influencing the individual, the blood, because 

 of its unquestionably close relation to inflammatory reactions, and 

 because of the ease with which it could be obtained and studied, 

 claimed the first and closest attention. The bactericidal properties 

 or normal blood serum noted in 1886 by Nuttall, 20 v. Fodor, 21 and 

 Fliigge, moreover, aided in pointing to this tissue as primarily the 

 seat of the immunizing agents. It is an interesting historical fact, 

 that, long before this time, the English physician Hunter had noted 

 that blood did not decompose so rapidly as other animal tissues. 



The study of the blood serum of immunized animals as to simple 

 changes in chemical composition or physical properties has shed little 

 light upon the subject. Beljaeff 22 in a recent investigation found little 

 or no alteration from the normal in the blood sera of immunized 

 animals as to index of refraction, specific gravity, and alkalinity. 

 Joachim 23 and Moll agree in stating that immune blood serum is com- 

 paratively richer in globulin than normal serum. Similar observations 

 had been made by Hiss and Atkinson 24 and others. Important and 

 significant as these purely chemical observations are, they have helped 

 little in explaining the nature of the processes going on in immune 

 sera. The first actual light was thrown upon the mysterious phenomena 



20 Nuttall, Zeit. f. Hyg., i, 1886. 



21 v. Fodor, Deut. med. Woch., 1886. 

 "Beljaeff, Cent. f. Bakt., xxxiii. 



23 Joachim, Pfliigers Archiv, xciii. 



- 4 Hiss and Atkinson, Jour. Expcr. Med., v, 1900. 



