98 ACTIVITIES OF BACTERIA. 



unstable, and are rendered inactive by a temperature of 

 55 or by the action of sunlight. 



Recently statements regarding heat=resisting sub- 

 stances which are injurious to bacteria, and which differ 

 from alexins, have multiplied (Lowit, Bail). These ap- 

 pear to belong to the nuclein compounds, 1 and are particu- 

 larly produced from lymph-glands. 



Besides the bactericidal alexins, frequently agglutinin 

 and antitoxic substances (for example, against diphtheria) 

 are demonstrable in healthy individuals as congenital. 



An increase of the congenital resistance to various 

 infectious diseases has been sought and obtained in many 

 ways. Favorable effects sometimes against one, some- 

 times against several infectious diseases have been obtained 

 by a number of investigators by injecting animals with 

 thymus extract, spermin, abrin (poisonous albuminous 

 bodies from the paternoster pea), papain (albumin-dis- 

 solving ferment from papaw-tree) ; also cinnamic acid, tri- 

 chlorid of iodin, carbonate of sodium, 2 etc. 



Recently there has been discovered a protective action 

 against tetanus and botulism through injections of brain 

 substance (Wassermann and Takaki, Kempner), and against 

 typhoid through injection of spleen substance (Aujeszky). 



IV. Acquired Specific Immunity and Its Causes. 



There is a sharp contrast to this heightened resistance, 

 according to most authors, and the specific immunity 

 against a definite disease, which originates when an 

 attack of the disease is acquired and recovered from 

 spontaneously or when it follows purposeful injection 

 (active immunity): 



a H. Kossel has shown that less than a 0.5% solution of albumin pre- 

 cipitating nucleinic acid (obtained from calves' leukocytes) has strong 

 bactericidal action. Yet the nucleinic acid could scarcely explain the 

 alexin action. Previously (1893) Vaughan and MacClintock recog- 

 nized nuclein as destructive to germs. 



2 According to Fodor, an increase in the alkalinity of the blood 

 is accompanied by an increased resistance to many bacteria, but, 

 according to Fodor and Rigler, also every introduction of toxin is fol- 

 lowed by a decrease, and every introduction of antitoxin by an in-, 

 crease, in alkalinity (C. B. xxi, 134). 



