474 IMMUNOLOGY 



ing dose eighteen or more days later and found all of the rabbits 

 actively sensitized. The technique recommended by Manwaring is, 

 perhaps, the best for sensitizing dogs. Bally employed it in his 

 work in rabbits mentioned above. Using this method, Sherwood 

 and Stoland (1929) found the incubation period in dogs to vary 

 from nine to fourteen days after the second injection of horse 

 serum. 



Duration of the Hypersensitive State. — The duration of hyper- 

 sensitiveness in guinea pigs probably persists throughout the life- 

 time of the animal. Coca (1927) states that rabbits remain sensi- 

 tive, following a single injection of antigen, for about three weeks. 

 Bally (1929) observed the hypersensitive state to persist in rab- 

 bits as long as seventj'-seven days after two sensitizing doses of 

 horse serum. 



Shocking' Dose of Antigen, — The shocking dose of antigen is the 

 dose of antigen administered to produce symptoms of anaphy- 

 laxis. When given subcutaneously, large doses must be em- 

 ployed. The best results are obtained when it is administered 

 intraperitoneally or intravenously, although the subdural and 

 intracerebral routes may be employed. The shocking close should 

 be considerably larger than the minimum sensitizing dose of the 

 antigen. 



While it is necessary to employ a complete antigen to sensitize 

 an animal, it has been shown by Tomcsik and Kurotchkin (1928), 

 and by Avery and Tillett (1929) that anaphjdactic shock can be 

 produced in guinea pigs passively sensitized to specific bacteria 

 by injecting the carbohydrate specific for the bacteria in ques- 

 tion. In this work it has been found important to use antibac- 

 terial serum from rabbits since immune serum from horses yields 

 negative results. 



Goodner and Ilorsfali (1937) inferred from their studies on 

 anaphylactic shock in guinea pigs rendered passively sensitive to 

 pneumococcal capsular polysaccharide that the ratio of antigen 

 to antibody is very important. If the proportion of carbohydrate 

 is slightly in excess of the amount necessary to satisfy the avail- 

 able antibody, a fatal response is possible. If the antigen is 

 present in excessively large proportion, the result will be neg- 

 ative as is the case when the amount of antigen is too small. 



