TUBERCULOSIS TUBERCULIN THERAPY 719 



cent, aqueous solution. Filter. The last filtrate is von Ruck's tuber- 

 culin. 



7. Dixon's Tubercle-bacilli Extract. 1 Dixon has prepared a tuber- 

 culin by treating cultures of tubercle bacilli with ether and extracting 

 in salt solution. This has yielded good results in the treatment of tuber- 

 culosis. This product is prepared from the living organisms. The 

 tubercle bacilli are grown on 5 per cent, glycerin veal broth for a period 

 of from six to eight weeks at a temperature of 37.5 C. They are re- 

 moved from the incubator and collected on hard filter-paper. The 

 filtrate of glycerin broth on which they are grown is discarded. An 

 equal quantity, by weight, of tubercle bacilli of the bovine and human 

 type is used. The mass of organisms is partially freed from excess of 

 moisture by placing it between two sterile filter-papers, after which it is 

 placed in a dish in the incubator for from twenty-four to forty-eight 

 hours. The dried organisms are then washed in an excess of ether, 

 which is allowed to act until it has removed all the water and glycerin. 

 The organisms are then subjected to an excess of fresh ether and washed 

 in this for six hours, to soften the wax of the bacilli. This fat separates 

 so that it collects at the bottom of the vessel and is removed with a 

 Pasteur pipet. After the second addition of ether has been removed the 

 mass is allowed to dry until no ether odor is perceptible. After the mass 

 of tubercle bacilli has been thoroughly dried it is ground in a mortar and 

 suspended in physiologic salt solution in the proportion of 1 part of the 

 ground mass to 5 parts of an 8 per cent, salt solution. This suspension 

 is shaken in a shaking machine for from eight to ten hours, and is then 

 allowed to stand for several days at room temperature. It is finally 

 passed through impervious bacteria filters several times and the filtrate 

 examined microscopically, bacteriologically, and physiologically. Cul- 

 ture tests are made to determine its freedom from contaminating organ- 

 isms, and guinea-pigs are inoculated to ascertain that it contains no 

 living tubercle bacilli. One cubic centimeter of this extract represents 

 0.2 gm. of the organisms, and is known as the stock solution, from which 

 serial dilutions are made. This solution is sterile, but 0.5 per cent, of 

 phenol (carbolic acid) is added as a preservative to prevent subsequent 

 contamination. 



While the tuberculins just described are those mainly used, many 



others have been prepared and advocated in the diagnosis and treatment 



of tuberculosis. The aim is always to obtain the specific substances, 



with as little as possible of the toxic substances not only those con- 



1 Penna. Health Bull, 1914, No. 28, April. 



