HYPERSENSITIVENESS 473 



and arsphenamine respectively. Landsteinor and Chase (1937) 

 report upon anaplniaxis in animals induced by picryl chloride 

 and 2 A dinitrochlorobenzene. In their opinion their results 

 offer strong evidence that antigenic conjugates are formed fol- 

 lowing the application of substances of sim]ile chemical constitu- 

 tion. That is to say that the simple clicmical substances used 

 probably formed conjugates Avith \ho animals' own proteins, 

 forming ncAV antigens. The ])resence of these new antigens resulted 

 in sensitization. 



Sensitizing Dose of Antigen. — The initial or sensitizing dose 

 or doses of antigen may be introduced by injecting the material 

 into the tissues, blood stream or body cavity. Sensitization 

 through the respiratory and alimentary tracts has also been dem- 

 onstrated. This indicates that under certain conditions sufficient 

 antigen may be al)sorbed through either the respiratory or in- 

 testinal epithelium to bring about sensitization. Rosenau and 

 Anderson found that the sensitization of one guinea pig was ac- 

 complished by the injection of 0.000,001 c.c. (one millionth) of 

 horse serum. Coca (1927) says that guinea pigs have been actively 

 sensitized with as little as 0.000,000,5 gram of crystalline egg 

 albumen. He further states that it requires from 1,000 to 10,000 

 times as much antigen to sensitize rabbits as guinea pigs. 



Incubation Period in Active Sensitization. — The incubation 

 period in active sensitization is the period of time between the 

 administration of the sensitizing dose and the development of 

 hypersensitivene.ss. In guinea pigs this varies from five to ten 

 days. It has been observed that the smaller the sensitizing dose 

 employed the longer tlie incubation period. Coca (1927) says 

 that it may l)e as long as nineteen to twenty-five daj's Avhere 0.000,1 

 lo 0.000,01 c.c. of ox serum is used. Rabbits and dogs arc more 

 dit^cult to sensitize than guinea pigs. Auer (1915) recommends 

 that rabbits be given four to eight injections of antigen sub- 

 cutaneously four to eight days apart. He quotes Arthus as find- 

 ing the incubation period to ])e from eight to fifteen days after the 

 last injection. 



Bally (1929) working in this laboratory succeeded in sensitizing 

 ra])bits to horse serum by administering 0.5 c.c. per kilogram of 

 body weight subcutaneously followed in forty-eight hours by 

 an intravenous injection of the same amount. He gave the shock- 



