896 DISEASES CAUSED BY FILTRABLE VIRUS 



"seed virus" obtained from the vesicles of human vaccinia. This 

 method of using humanized virus for the inoculation of calves for 

 vaccine production is preferred by many workers and is spoken of 

 as "retrovaccination. " 



Park 14 believes that the most efficient and reliable seed virus con- 

 sists of what he calls human-calf -rabbit seed virus. Crusts from 

 healthy children, nineteen days after vaccination, are collected. 

 These are cut up and emulsified with boiled water. With this an 

 area of about six inches square is inoculated on a calf, the remainder 

 of which is vaccinated the ordinary way. The virus from this 

 space is separately collected and, after being glycerinated, is used 

 in dilution of 1 to 12i/> parts of salt solution to vaccinate rabbits 

 on the shaven skin of the back. The pulp from this rabbit vaccina- 

 tion is then used for calf vaccination. 



Actual vaccination of the animals is done as follows: Calves 

 which have been kept under observation for at least a week are 

 thoroughly washed and cleaned and the abdomen is clipped and 

 shaved over an area extending from the ensiform cartilage to the 

 pubic region, including the entire width of the belly and the inner 

 folds of the thighs. It is best to shave the animal a day or two 

 before vaccination so as to avoid fresh scratches and excoriations. 

 Just before actual operation the animal is strapped to a specially 

 constructed operating table in such a way as to allow free access 

 to the shaved area. This area is now thoroughly washed with soap 

 and water followed by alcohol, or, in some institutes, by a weak 

 solution of lysol. If the latter is used, the field of operation must 

 again be thoroughly rinsed with sterile .water. About a hundred 

 small scarifications are made in this area, preferably by crossed 

 scratches, covering for each scarification an area of about 3-4 square 

 centimeters. Into these areas the virus is rubbed, using for each 

 small area a quantity about sufficient to vaccinate three children. 

 Two to three centimeter spaces are left between the lesions. The 

 lesions are then allowed to dry and may be covered with sterile 

 gauze or, as in Vienna, with a paste made up of beeswax, gum arabic, 

 zinc oxid, water, and glycerin. In some institutes the lesions are 

 left entirely uncovered. 



Ordinarily within about twenty-four hours after vaccination a 

 narrow pink areola appears about the scratches. Within forty-eight 



14 Park and Williams, Path. Microorg., N. Y., 1914, p. 569. 



