THE MANUFACTURE OF ANTISERA 749 



equivalent of 0.25 g. of Koch's Old Tuberculin per 500 g. weight guinea- 



pig- 



Conclusions may be drawn from such tests according to the follow- 

 ing suggestions made by the Bureau of Animal Industry: 



If the tuberculin which is provisionally taken as the standard kills 

 not less than two-thirds of the sensitized guinea-pigs injected with it 

 before the lapse of twenty-four hours, and the two normal guinea-pigs 

 injected with it remain free from symptoms of disease excepting the 

 rapidly passing distress which may immediately follow the injection, 

 it is required that any other sample of tuberculin, if it possesses a re- 

 liable degree of potency, should kill, within twenty-four hours, at least 

 half the sensitized guinea-pigs injected with it, and that the normal 

 guinea-pigs injected with it should be alive and well at the end of 

 twenty-four hours. 



In human, as well as in veterinary practice, tuberculin may be 

 applied as a diagnostic agent in various ways. In addition to the hypo- 

 dermic injection of tuberculin (old), as described above, the method of 

 Calmette,* von Pirquetf and MoroJ may be used in human practice. 

 Calmette's ophthalmo test consists in the instillation in the eye of 

 Koch's purified or refined tuberculin. Purified tuberculin is prepared 

 by treating the original tuberculin with absolute alcohol, washing and 

 drying the precipitate. One drop of a i per cent solution of purified 

 tuberculin is placed in the eye. A positive reaction is manifested by a 

 congestion of the palpebral and ocular conjunctiva a few hours after the 

 application of the tuberculin. The method of von Pirquet* depends 

 upon the cutaneous application of the tuberculin. One drop of tuber- 

 culin (old) is placed on the arm, after cleansing the skin, and the small 

 area under the drop is scarified. Two or more small areas may be 

 treated in this way, as well as a control area treated with sterile salt 

 solution or a solution of glycerin and dilute carbolic acid in substitu- 

 tion for the tuberculin. The appearance of a reddish zone in from 

 twelve to twenty-four hours indicates a positive reaction. This area 

 of inflammation gradually increases somewhat in elevation and diameter 

 and finally subsides in a few days. Moro's modification of von Pir- 

 quet's method consists in the use of tuberculin ointment prepared by the 

 combination of tuberculin (old) and anhydrous lanolin in equal parts. 



* Calmette, Presse Medicale, 1907, 15. 

 t von Pirquet, Berl. klin. Woch., 1907, 44. 

 j Moro, Mfinch. med. Wch., 1908. 



