LEPROSY BACILLUS. 617 



quently shows a beaded appearance (degeneration 

 forms ? ) . It is said to take up dyes more readily 

 than the tubercle bacillus, but the difference is not 

 so great as to be distinctive. It stains by Gram's 

 method. 



Duval has recently succeeded in cultivating the 

 leprosy bacillus on media prepared as follows : 



The rind was carefully removed from the fruit portion cultivation. 

 of fully matured green bananas, every precaution to 

 avoid contamination being used, and large blocks of the 

 fruit, after slanting one surface with a sharp knife, were 

 introduced into suitable sterile glass cylinders provided 

 at the bottom with cotton plugs saturated in sterile dis- 

 tilled water. These plugs served not only as support for 

 the banana, but as a source of constant supply of mois- 

 ture. Sterile 1 per cent, solutions of tryptophan, cystein 

 (made from protein), and leucin were next prepared and 

 a portion of each poured on and allowed to saturate the 

 banana. These solutions were used separately and in 

 varying combinations, in order to determine on which 

 the B. leprce would grow best or grow at all. Both the 

 banana and agar, which was saturated in a 1 per cent, 

 solution of cystein, proved an excellent medium for the 

 artificial cultivation of the leprosy bacilli when incu- 

 bated at from 32 to 35 degrees C. The maximum growth 

 occurred at a temperature of 32 degrees C. Light seems 

 to favor the growth of B. leprw; cultures kept in a glass 

 incubator regulated at 32 degrees C. grew more rapidly 

 than those in the dark chamber under similar conditions. 

 Multiplication began early in the transplants and visible 

 growth developed in the form of small, glistening, white 

 colonies in from four to six weeks. Growth also occurred 

 on the banana and agar when a solution of cystein and 

 tryptophan had been added. The fact that growth 

 occurred on the protein-cystein medium, and not on the 

 others except in the presence of it, shows very conclu- 

 sively that B. leprcc utilizes the end-products of digestion 

 and not the products of cell metabolism. At least it is 

 reasonable to assume that this is the case, if deductions 

 may be drawn from these experiments. Multiplication 



