S68 MICROBIOLOGY OF SPECIAL INDUSTRIES 



developed methods of preparation and distribution, so that any phy- 

 sician may purchase the vaccine and administer it to his patients. 



Hogyes* substituted dilutions of the "fixed virus" for the dried 

 spinal cords. For the initial treatment, a few cubic centimeters of a 

 1 : 10,000 dilution was used. In the succeeding injections graduated 

 dilutions were employed. While the work of Hogyes has been con- 

 firmed by other investigators, the method is not generally regarded 

 as possessing the safety of the original Pasteur treatment, -i 



Harris f has devised a simple method of preparing the vaccine by 

 iEreezing the infected spinal cord of the rabbit with CO2 snow, and then 

 drying the material in vacuo over sulphuric acid at a temperature of 

 10° to 15°. 



The product is kept in the refrigerator in hermetically sealed vials. 

 It is claimed that the material so prepared maintains its original 

 strength or infectivity several months. 



Cummings't method consists in the dialysis of the rabic material 

 in standard suspensions. Dialysis for twelve to twenty-four hours 

 possesses the advantage of destroying the infectivity of the virus, 

 without disturbing its immunizing properties. 



DoRSET-NiLKS (Hog-Cholkra) Serum.§ — To prepare the material 

 for this process of immunization it is first necessary to secure a virulent 

 strain of hog cholera virus. This may be obtained from any t3^ical 

 outbreak of the disease. A specimen of blood may be drawn, asep- 

 tically, from the carotid artery of a pig suffering from the disease, and 

 tested for activity. Frequently a given strain of virus may not produce 

 the acute form of hog cholera. In attempting to raise the virulence of 

 a relatively weak virus it may be passed through a series of young pigs 

 until it uniformly produces symptoms after four to six days' incubation 

 and death in less than fifteen days. None except a virus having this 

 degree of activity should be used in manufacturing the hyperimmune 

 serum. 



The virulent blood used, in the process of hj^erimmunization 

 should be obtained from susceptible pigs weighing from 25 to 50 kg. 

 (50 to 100 pounds) each. The animals to be used as the"hjrperim- 



* Hogyes, Acad, des Sciences de Budapest, Oct. 17, 1897. 

 t Harris, Jour. Infect. Dis., 1912, 10, p. 369. 



J Proceedings isth International Coiigress on Hygiene and Demography, Washington, 

 D. C, 1912. 



§_U. S. Bureau of Animal Industry, Bull. No. 102. 



