270 THE PRINCIPLES OF IMMUNOLOGY 



and obtained potent sera against the rinderpest virus. Of 3318 animals 

 treated with this serum 455 or 13.9 per cent, died, while the mortality 

 among non-treated animals averages between 85 per cent, and 95 per 

 cent. The serum can be used prophylactically in doses of 100 to 200 

 c.c. If the virus is simultaneously injected in small doses as advised 

 by these authors, the results appear to be extremely satisfactory. 

 The serum for curative purposes should be employed within thirty days 

 after the onset of fever. 



Anti-hog-cholera Serum. Immunization against hog cholera has 

 an important historical as well as a practical bearing since it was in this 

 disease that the first attempt to immunize with bacterial products was 

 made. Salmon and Theobald Smith published in 1884 their account 

 of the production of immune sera in the pigeon by the inoculation of 

 killed broth culture of the bacillus of hog cholera. Subsequent studies 

 have made it appear that the disease is not due to the bacillus of hog 

 cholera and much evidence is at hand to support the view that the 

 etiological agent is a filterable virus. At the present time immunity is 

 produced in healthy hogs by the injection of blood obtained from 

 infected hog's, thus implanting the virus. It is necessary to protect 

 the animals employed by passive immunization with a previously- 

 prepared antiserum. The animals selected are injected subcutaneously 

 with 40 c.c. of anti-hog-cholera serum per hundred pounds of weight. 

 Two to three days later the animals receive intravenously 3 or 4 c.c. 

 of defibrinated blood obtained from an animal suffering from the 

 disease, or the animals may be exposed in infected pens. If the animals 

 survive, after a period of one month they are given 5 c.c. of the living 

 virus. This is repeated after two or three weeks. The immunized 

 animals are bled from the tail. Five cubic centimeters of blood per 

 pound of weight are usually withdrawn. The protective power of the 

 serum thus obtained is then determined in a series of hogs. For 

 prophylactic purposes the* animals receive 40 c.c. subcutaneously per 

 hundred pounds of weight or simultaneous injections of virus and 

 serum, but this combination is not without danger. For therapeutic 

 purposes several injections are necessary and the serum should be 

 administered as early as possible. 



THERAPEUTIC USE OF NORMAL SERUM 



Normal serum therapy in man has included the use of both human 

 and animal sera. In the treatment of natural or experimental disease 

 in man or animals the normal serum employed may be homologous or 

 heterologous. The basis of such method of treatment has often been 

 entirely empirical, but as serum therapy has been more carefully 

 studied the employment of normal serum may be placed in two cate- 

 gories, namely that of the non-specific protein treatment of disease 

 or that of providing the blood with certain elements necessary for the 

 process of clotting. It is to be conceded that a normal serum may be 

 employed because of some natural antibodies which it may contain, 

 but such a form of passive immunization is much improved if the 



