202 INFECTION AND IMMUNITY 



nephrotoxin could not be upheld and the subject is still in the ex- 

 perimental stage. 



Recent experiments by Pearce 1 suggest that at least a part of the 

 local injury to organs exerted by such "cytotoxic" sera may not be 

 due to a specific action upon the organ cells so much as upon the 

 hemagglutinating action of the sera causing embolism and necrosis. 



It is a fact also that most cytotoxic sera are usually hemolytic as 

 well. It is not easy to decide, therefore, how much of the action upon 

 the organs is due to their true cytotoxic properties and how much is 

 attributable to the concomitant action upon blood cells. The extrav- 

 agant hopes at first based upon cytotoxin investigation, especially in 

 regard to the problem of malignant tumors, have been disappointed, 

 and much is still obscure in regard to the cytotoxins which> calls for 

 further research. 



The many points of similarity existing between bacterial toxins and 

 digestive ferments, by animal inoculation, suggested to several observ- 

 ers the possibility of producing antibodies against the latter. As a 

 result, a number of antiferments have been obtained, chief among which 

 are antilab (Morgenroth 2 ) , antipepsin (Sachs 3 ) , antisteapsin (Schiitze 4 ) , 

 and antilactase (Schiitze). 



The stimulation of antibody formation in the sera of animals is a 

 consequence, therefore, of the injection of a large variety of substances 

 some of them poisonous, some of them entirely innocuous. The sub- 

 stances possessing this power have been conveniently named antigens or 

 antibody-producers by German writers. The term antigen though ety- 

 mologically wrong, nevertheless is convenient and has crept into general 

 usage. It signifies simply a substance which can stimulate the pro- 

 duction or formation of an antibody. Such substances, so far as is 

 known, belong to the group of proteins and are derivatives of animal or 

 plant tissues. Being proteins, all antigens are colloids. Recently, how- 

 ever, some crystalloidal substances have been described as possessing 

 antigenic properties. 



1 Pearce, Jour. Exper. Med., viii, 1906. 



2 Mwgenroth, Cent. f. Bakt., 1899. 



3 Sachs, Fort. d. Med., 1902. 



*Schiitze, Deut. med. Woch., 1904; Zeit. f. Hyg., 1905. 



