184 ACTIVE IMMUNIZATION 



abandoned, animal lymph being exclusively used. This is prepared 

 in special laboratories, and put up in such form that the practitioner 

 can carry out the vaccination at any place, whereas in former years 

 the persons who were to be vaccinated were often obliged to come 

 to the stables in which the animals that furnished the lymph were 

 kept. 



Preparation of the Vaccine. The technique employed in the prepa- 

 ration of the vaccine is in brief the following (method in use at the 

 Government Vaccine Institute of Vienna). The animals used are 

 young cattle, not older than two years or younger than six months, 

 whose freedom from disease has been previously ascertained. After 

 being placed on the operating table the abdomen up to the umbili- 

 cus, as also the portion of the inner surface of the thighs, is shaved, 

 the skin cleansed with green soap and water, then copiously rinsed 

 with a 2 per cent, lysol solution, then with sterile water, and finally 

 dried with sterile gauze. The entire surface is then scarified in 

 longitudinal or transverse streaks, measuring about 10 cm. in length, 

 and from 2 to 2.5 cm. apart, care being taken that the papillary 

 layer is just barely touched, so that there is no bleeding. The virus 

 is then introduced into these streaks, either by making use of a 

 special vaccine lancet (Chalybaeus lancet) or by rubbing it with 

 a suitable instrument. 



In Vienna, where so-called retrovaccination lymph is exclusively 

 prepared, calf lymph is first inoculated into a healthy child, when 

 lymph from this source is employed to inoculate the new animal; 

 the resultant material is termed retrovaccine of the first generation. 

 This can then be used for human vaccination, or, still better, the 

 product obtained with it from a second animal the so-called retro- 

 vaccine of the second generation. 



After the animal has been prepared, as just described, the entire 

 vaccinated surface is suitably protected against dirt and infection, 

 and the animal returned to its stable, which is kept scrupulously 

 clean. The result is seen in Fig. 11, which represents the appearance 

 of the "pox" at the end of five days. At this time, or after three to 

 four days in young animals, the covering is removed, the entire 

 surface cleansed, as described before, but not dried, when with the 

 aid of a stout curette the surface material is scraped off, care being 

 taken that it is not contaminated with blood. With practice the 

 vesiculated epithelium can be removed in long strips. The material 



