SEROLOGY — MANUFACTURE AND USE OF SERA AND VACCINES 273 



which has been filtered to remove the germs. It is a toxin solution and 

 not a bacterin proper. 



B. Tuberculin Residuum (T. R.).— This is prepared by grinding the 

 dried tubercle bacilli, extracting with water, centrifugalizing, discarding 

 the supernatant liquid, regrinding the sediment, which is first allowed to 

 dry, and mixing with glycerin and water. It is thus a suspension of 

 pulverized tubercle bacilli in an aqueous solution of glycerin. The grind- 

 ing process is tedious and requires much time. The tuberculin is 

 standardized so that i cc. will represent 10 mg. of the dry culture. 



The supernatant hquid, after centrifugalizing, is sometimes drawn off, 

 instead of rejecting, and constitutes the upper tuberculin (T. O. ) (Obere 

 Tuberculin). These two tubercuhns (the T. R. and the T. O.) differ in 

 therapeutic value and in physical properties. 



C. Bacillus Emulsion (B. E.). — ^This consists of pulverized tubercle 

 bacim suspended in 50 per cent, glycerin and is standardized to contain 

 5 mg. of solid matter per cc. It differs from T. R. in that the supernatant 

 liquid (T. O.) is not drawn off. 



D. Tuberculin Precipitate (T. R.).— This is obtained from old tuber- 

 culin by precipitation with alcohol, drying and pulverizing the precipitate. 

 It is used in making the Calmette eye-test. (See tuberculosis). 



E. Bouillon Filtrate (Tuberculin Filtrate B. F.— Denys Tuberculin). 

 The tubercle bacillus cultures are passed through a Berkefeld filter to 

 remove aU germs. The filtrate is preserved with trikresol. 



9. Small-pox Vaccine 



Small-pox vaccine is not a true toxin nor yet a true bacterin. Its 

 value in the eradication of small-pox has world-wide recognition. The 

 following is the manner in which small-pox vaccine is prepared. 



a. Selecting the Animal.— A young heifer (five to ten months old) is 

 selected, tested for tuberculosis by means of tuberculin. The animal is 

 observed for a time to make sure of general condition of health; is weU fed 

 and well cared for, under conditions as sanitary as it is possible to keep 



them. , , , 



b Inoculating the Animal.— The heifer is strapped securely to a frame- 

 work back dowA, the udder region is cleansed, shaven and cross marked 

 (scarified) with a sharp scalpel. The cuts are just deep enough to cause 

 • the escape of serum, not actual bleeding. This scarified surface is then 

 inoculated with glycerinated smaU-pox virus taken from a patient. When 

 the inoculated material has had time to be absorbed the animal is righted 

 again and cared for under as aseptic conditions as possible. In time 

 (six to seven days) pustules form over the entire inoculated area. The 

 virulent virus from man conveys the disease to the ammal, but m its 



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