1923] Wagencr: Leishmania tropica ami Leishmania infantum 481 



irre^larly shaped red halo, which faded to a flesh color beyond the 

 edge of the indurated area (pi. 42, fig. 4). The areas of induration 

 varied from 5 to 7 mm. in diameter on the different immune rabbits. 

 At about the fifth day these white centers formed a hard, yellowisli 

 browTi crust, which sloughed off three or four days later without 

 leaving a scar. 



Neither the white center nor the area of induration was present 

 in the control tests made on each rabbit with the extracting fluid 

 (pi. 42, fig. 4&) or in any of the tests on the normal rabbit. 



This reaction is comparable to that produced in tubercular animals 

 by the intradermal injection of Old Tuberculin, which results in a 

 red and indurated papule with a central necrotic area which sloughs 

 off several days after the injection. 



Krause and Peters (1920) demonstrated a local reaction to 

 tuberculosis re-infection when living tubercle bacilli were injected 

 intracutaneously into guinea pigs. This reaction was characterized 

 by a reddened papule, rapid ulceration, and slough followed by 

 healing. These authors considered this an immune reaction in the 

 guinea pigs. As this reaction corresponds very closely to that 

 obtained in the rabbits immunized to Leishmania, an attempt was 

 made to further correlate the results by injecting into an immune 

 and a normal rabbit cultures of the living flagellates. These injections 

 were made intradermally on the testicle, this site being chosen on 

 account of the thinness of the epidermis and also because Laveran 

 (1917) had found it possible to produce Bagdad boils in white mice 

 by injecting cultures of Leishmania tropica into the testicular sac. 

 The rabbits were observed daily for a week and frequently there- 

 after. No reaction occurred. The reason, probably, was because, 

 as suggested by Delanoe (1911), the living flagellates were being 

 rapidly phagocytized. 



One week after the first series of skin tests had been applied to 

 the immune rabbits, they were retested in order to standardize more 

 definitely the alkaline extracts of L. tropica and L. infantum. This 

 was considered necessary because throughout the first tests the extract 

 from L. infantum had produced in general a less marked reaction 

 than that from L. tropica. This difference might have been due to 

 an unequal concentration of protein because of the slightly larger 

 size of L. tropica as compared with L. infantum. Hence extracts 

 made by the addition of a definite number of flagellates per c.c. would 

 not necessarily represent equivalent amounts of protein. Flagellate 



