458 CHOLERA 



the normal peritoneal fluid. A control experiment should accordingly 

 be made with '001 c.c. of normal serum in place of the anti-cholera serum. 

 If no alteration of the organism occurs with its use, then the conclu- 

 sion is that a true reaction has been given. Corresponding bacteriolytic 

 effects may be obtained by in vitro methods, introduced since Pfeiffer's 

 original method (p. 534). 



The serum of an animal immunised by the above method has 

 also marked agglutinative and other anti-bacterial properties 

 (p. 541) against the cholera spirillum, and these properties closely 

 correspond with Pfeiffer's reaction as regards specificity. Such 

 a serum has, however, little protective effect against the toxic 

 action of the dead spirilla, and Pfeiffer maintains that little or 

 no antitoxin to the endotoxin can be produced. On the other 

 hand, Macfadyen, by injecting the endotoxin derived from the 

 spirilla by grinding, obtained a serum which had antitoxic as well 

 as agglutinative and bacteriolytic properties (vide Immunity). 

 Metchnikoff and others have also obtained antitoxic sera which 

 act on the extracellular toxins obtained by filtration. 



The serum of cholera convalescents has been found to possess 

 protective and increased bactericidal action. These properties of 

 the serum may be present eight or ten days after the attack of 

 the disease, but are most marked four weeks after ; they then 

 gradually diminish. Specific agglutinative properties have, how- 

 ever, been detected in the serum of cholera patients at a much 

 earlier date, in some cases even on the first day of the disease, 

 though usually a day or two later. The dilutions used have 

 been usually 1 : 15 to 1 : 120, and these had no appreciable 

 effect on organisms other than the cholera spirillum (Achard and 

 Bensande). In some cases, however, the agglutinative property 

 may not appear after recovery. Variations in the opsonic index, 

 analogous to those in other diseases, have recently been observed 

 in cholera, a marked fall on the acute onset of the disease being 

 a noteworthy feature. 



Within recent times there have been introduced for therapeutic 

 purposes several so-called anti-sera which are supposed to be anti- 

 toxic as well as anti-bacterial, and of these the two most ex- 

 tensively used are those of Kraus and SchurupofF. Reports 

 regarding the effects of these sera during the Russian epidemic 

 are of somewhat conflicting character, but in any case it cannot 

 be said that they have a markedly beneficial action. They have 

 further been critically examined by others, who deny to them any 

 marked antitoxic action when tested experimentally. While, 

 therefore, it may be admitted that antitoxins to some of the 

 cholera toxins may be obtained, yet Pfeiffer's position, that 



