336 PROTECTIVE INOCULATIONS. 



spiratory passages. Subcutaneous injections cause a painful local 

 tumefaction, often followed by an abscess, but without the general 

 symptoms of influenza. 



Experiments have been made in Germany by Hell, Siedamgrotzki, 

 and others, which indicate that the subcutaneous injection of blood 

 serum from immune horses may confer immunity on other horses. 

 Hell usually injected forty cubic centimetres at a time, and repeated 

 this at intervals until two hundred to two hundred and forty cubic 

 centimetres had been injected in the course of two or three weeks. 

 He also reports the results of treatment by injections of blood serum 

 into the trachea in horses already infected, and thinks these injections 

 had a favorable influence on the course of the disease. Experiments 

 made subsequently by Toepper have given a similar result, but others 

 have not been so fortunate, and the immunizing value of blood-serum 

 injections, as practised by the authors referred to, seems to be still a 

 matter of some doubt. Toepper (1893) gives full directions for col- 

 lecting the serum and a detailed account of results of experimental 

 inoculations made by himself and others. He prefers to inject the 

 serum into the breast over the ensiform cartilage. No reaction oc- 

 curs after the injection. 



PLEURO-PNEUMONIA OF CATTLE. 



Protective inoculations against this disease have long been success- 

 fully practised. For this purpose serum obtained from the lungs of 

 an animal recently dead has been employed, this having been proved 

 by experiment to be infectious material, although the exact nature of 

 the infectious agent present in it was not determined. 



Willems, who w r as one of the first to advocate the use of protective 

 inoculations in pleuro-pneumonia (1852), gave a lecture in 1894 in 

 which he reviewed the evidence in favor of these inoculations in 

 the disease under consideration. Various methods had been em- 

 ployed. Thus Willems states that the natives of the banks of the 

 Zambeze cause animals to swallow a certain quantity of the liquid 

 from the pleural cavity of an animal recently dead, and thus give 

 them immunity. The virus has been injected into the circulation by 

 some experimenters, and others have )roposed to attenuate it by heat. 

 But the method which has been most extensively employed is that 

 discovered by the Dutch settlers at the Cape of Good Hope (the 

 Boers), and consists in inoculating animals in the tail with serum 

 from the lungs of an animal recently dead ; or with a virus obtained 

 from the tumefaction produced by such an inoculation in the tail. 



