768 Leprosy 



some symbiotic organism, such as the colon, typhoid, proteus, 

 or other bacilli, added. Or if the tissue were already con- 

 taminated the lepra bacilli proceeded to multiply. Duval 

 interprets this to mean that the lepra bacillus is unable to 

 effect the destruction of the albumin molecule alone, and hence 

 explains the advantage of adding tryptophan. The medium 

 most successfully employed by Duval is as follows : 



" Egg- albumen or numan blood-serum is poured into 

 sterile Petri dishes and inspissated for three hours at 70 C. 

 The excised leprous nodule is then cut into thin slices, 2 to 4 

 mm. in breadth and 0.5 to i mm. in thickness, which are 

 distributed over the surface of the coagulated albumin. 

 By means of a pipet the medium thus seeded with bits of 

 tissue is bathed in a i per cent, sterile solution of trypsin, care 

 being taken not to submerge the pieces of leprous tissue. 

 Sufficient fluid is added to moisten thoroughly the surface of 

 the medium. The Petri dishes are now placed in a moist 

 chamber at 37 C., and allowed to incubate for a week or ten 

 days. They are removed from the plates from time to time, 

 as evaporation necessitates, for the addition of more trypsin. 

 It will be noted that after a week or ten days the tissue bits 

 are partially sunken below the surface of the medium and are 

 softened to a thick, creamy consistence, fragments of which 

 are readily removed with a platinum needle. On microscopic 

 examination of this material it is noted that the leprosy bacilli 

 have increased to enormous numbers and scarcely a trace of 

 the tissue remains. Separate lepra bacillus colonies are also 

 discernible on and around the softened tissue masses. . . . 

 The colonies are at first grayish white, but after several days 

 they assume a distinct orange-yellow tint. . . . Subcultures 

 may be obtained by transferring portions of the growth to a 

 second series of plates or to slanted culture- tubes that contain 

 the special albumin- trypsin medium. After the third or 

 fourth generation the bacilli may be grown without difficulty 

 upon glycerinated serum agar prepared in the following 

 manner : 



' Twenty grams of agar, 3 gm. of sodium chlorid, 30 c.c. 

 of glycerin, and 500 c.c. of distilled water are thoroughly 

 mixed, clarified, and sterilized in the usual way. To tubes 

 containing 10 c.c. of this material is added in proper propor- 

 tion a solution of unheated turtle muscle infusion. Five 

 hundred grams of turtle muscle are cut into fine pieces and 

 placed in a flask with 500 c.c. of distilled water. This is 



