DISEASES PRODUCED BY ULTRA-MICROSCOPIC ORGANISMS 481 



others has been practised, and has been found in some instances to 

 result in a low mortality. The method has been practically- 

 abandoned. Injections of the bile from animals having the disease 

 has been advocated by Koch and extensively practised in South 

 Africa, with good results. 



The common method of immunization against rinderpest is 

 that developed by Kolle and Turner. Animals which have recov- 

 ered spontaneously from an infection, or that have been im- 

 munized by injections of virulent blood and gall, are hyper- 

 immunized by repeated injections of virulent blood. The first 

 injection is of a liter of virulent blood. After the subsidence of the 

 reaction an injection of 500 c.c. is given, and later a third injec- 

 tion of a liter. A fourth injection may be made. The blood is 

 drawn from the jugular vein at three intervals, a week apart. 

 Another injection of a liter of virulent blood is given, and later 

 the animal is again bled. The serum, in amounts of 20 c.c., 

 should protect an animal against injection of 1 c.c. of virulent 

 blood. An injection of 50 to 100 c.c. of the serum so secured will 

 protect an animal against infection for a space of 2-4 months 

 usually. A more permanent immunity may be established by the 

 use of what is termed the " serum simultaneous " method. The 

 animal is injected on one side with 8 to 25 c.c. of the immune serum, 

 and on the other with 1 c.c. of virulent blood. Some animals react 

 by a distinct fever, others show no effect. The latter are rendered 

 immune for several months only, while the former for much longer 

 periods. The blood of the animals reacting is infective during the 

 period of fever. The vaccination mortality is about 1 per cent. 



Transmission. The disease is readily transmitted by means of 

 soiled food, water, and by direct contact. 



Virus of Hog-cholera 



Disease Produced. Hog-cholera, Schweinepest, swine fever. 



From the time of the researches of Salmon and Smith on this 

 disease, published in 1885, until 1904, the cause of hog-cholera was 

 believed to be the Bacillus cholera suis (B. suipestifer) . In the 

 latter year de Schweinitz and Dorset showed the typical hog- 

 cholera in the United States to be due to a filterable virus. This 

 has been confirmed by Hutyra, Uhlenhuth, and others in Europe. 

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