268 BACTERIOLOGICAL METHODS 



The bacterial contamination of smallpox vaccine has received 

 considerable attention on the part of American bacteriologists. 

 Such vaccines are rarely wholly free from extraneous bacteria, no 

 matter how carefully prepared. It is rather remarkable that the 

 method of manufacturing the vaccine is not modified in accordance 

 with modern progress in sanitation. Since the smallpox virus is 

 filterable it would seem possible to pass the dissolved material 

 through a porcelain or clay filter leaving behind the bacteria and 

 other undesirable foreign matter. The filtrate could be tested 

 for the possible presence of such bacteria as might have passed 

 through the filter and these destroyed by suitable agents (such as 

 will not interfere with the activity of the vaccine), and the 

 filtrate perhaps concentrated to the desired degree or perhaps used 

 in the liquid form. However, it is likely that the present method of 

 manufacture and use of the smallpox vaccine will continue for 

 some time. The marketed smallpox vaccine should contain but 

 few viable bacteria, not to exceed 200 per dry point or per gly- 

 cerinated tube. According to extensive tests made by Rosenau 

 in 1902-1903, dry points and glycerinated tubes contained as 

 high as 44,000 bacteria per point or tube, but tests made since 

 that time (Nelson and others) show much lower figures, ranging 

 from ten or fifteen to 300 bacteria per point or tube. Small- 

 pox virus should also be examined (occasionally at least) for the 

 presence of colon bacilli, streptococci, tubercle bacilli and the 

 tetanus bacillus. 



24. Special Biological and Toxicological Tests 



Arsenic in Foods and Medicines — ^Biological Test. — Arsenic 

 is widely distributed in nature and is extensively used in the arts 

 and industries. Medicinally it is a very popular tonic and is also 

 much used as an insecticide in the form of sprays and washes. 

 Animal hides are frequently preserved by arsenic which accounts 

 for the presence of this poison in gelatin made from such hides. 



