458 INFECTION AND IMMUNITY. 



The subject of acquired immunity to dysentery 

 is hardly on a satisfactory basis. The serum of 

 convalescents shows a distinct bactericidal and op- 

 sonic power for the organism, and there is good 

 reason to believe that the acquired immunity per- 

 sists for some time after the disappearance of the 

 bactericidal amboceptors and opsonins, an event 

 which takes place rather early. As in typhoid, 

 animals which through immunization have once 

 been stimulated to produce antibodies, form them 

 much more readily on the occasion of a subsequent 

 inoculation. This acquired facility in producing 

 antibodies may be a factor in acquired immunity. 

 By immunizing horses, serums of rather high pro- 

 tective power have been obtained. Kruse prepared 

 a serum of which 1/80000 gram would save a 

 guinea-pig from a dose of the bacilli which killed 

 a control in 20 hours. It is assumed that the pro- 

 tective power of this serum is due to its bactericidal 

 action. The antitoxic serum which Rosenthal pre- 

 pared, by immunizing with 30 days' old bouillon 

 cultures, protected not only against the toxin, but 

 also against the bacilli; and conversely an anti- 

 bacterial serum protected against the toxin (cited 

 by Lentz). Such results leave us very much in 

 doubt as to the existence of a true antitoxic serum. 



^e value of protective inoculations is not well 

 Therapy, established. Shiga at one time practiced mixed 

 active and passive immunization (bacilli plus im- 

 mune serum) on 10,000 individuals. This did not 

 decrease the number of infections, although a lower 

 mortality resulted. Shiga claims that the thera- 

 peutic use of his serum reduces the mortality to 

 one-third that of the untreated. The serum of 

 Kruse, and also that of Eosenthal, are said to be 



