NATURE OF THE ACTIVE PRINCIPLES ^25 



iiiittcd that tlie Forssnian antigen-]-antibody coiiibinations may 

 beliaxe similar to the other antit>en-|-antibocly combinations de- 

 scribed in this monograph. In connection Avith this assiunption, 

 the normal toxicity of heterologous sera may be discussed. 



The primary toxicity ot normal sera for heterologous animal 

 species is ^vell kno^vn. Toxic normal sera produce necrosis on 

 sid)cutaneous injection and acute shock and death following in- 

 tra\enous administration. The intraj^eritoneal injection elicits 

 a state of protracted shock (Aronson) . The toxic factors behave 

 as normal antibodies. They consist of thermo-labile amboceptor- 

 like and thermo-labile complement-like fractions (Aronson) . The 

 sidjstances can be removed by absorption Avith tissue extracts of 

 susceptible animals (Doerr and E. P. Pick, Aronson and others) ; 

 the tissue of the resistant animal failing to do so (Aronson) . There 

 is considerable e\'idence that the effect of the toxic factors of 

 normal serinn is closely allied to an antigen-|-antibody reaction, 

 the antibody Ijeing supplied by the serum injection and the 

 antigen by the animal receiving injection. The toxic normal 

 sera agglutinate and sometimes hemolyze the red blood cells of 

 the stisceptible animal. In some instances, toxic normal sera floc- 

 culate Avith the serum of the susceptible animal species. Thus, ox 

 sertim contains normal precipitins for guinea pig serum, goat 

 sertim for rabbit serum, etc. The causal relationship of the Forss- 

 man antigen-f-antibody reaction to the normal toxicity of sera is 

 highly suggestive. Normal rabbit serum has a marked toxicity for 

 guinea pigs which is increased when the rabbit is treated ^vith 

 the Forssman antigen. Forssman antigen is present in various 

 organs of the animals belonging to the guinea pig group. On the 

 other hand, there is a Avidespread occiurence of normal anti- 

 sheep hemolysins in the animals of the rabbit type. Friedemann 

 assimies that primarily the organs of all animals contain hetero- 

 phile antigen. In later development, as a response to the antigens, 

 antibodies are developed. In some species in which there is a 

 smplus of antigen and only Aveak antibody production, there 

 result conditions such as are foiuid in the guinea pig, cat, dog and 

 horse; but Avhen the antibody production is strong and the 

 amount of heterophile antigen is scanty, the latter may not be 

 demonstrable, and as a residt, the conditions may be as in the 

 rabbit (Davidsohn) . 



As may be remembered fr(jm pre\ ions studies, Avhole blood and 

 sera of a great variety of animal species possess no reacting po- 



