1923] Wagener: Leislnnania tropica and Leishmania infunluin 483 



growths from a number of cultures were therefore wa.shed oif in 

 saline and packed by rapid centrifugalization for one half-hour. 

 One part of the packed organisms was then diluted with four parts 

 of the alkaline extracting fluid, treated as before, and stored in the 

 ice box. It was then possible to make up any dilution desired from 

 these stock alkaline extracts of L. tropica and L. infantum. 



Tests made by the intradermal injection of 0.2 c.c. of these stock 

 alkaline extracts into the immune rabbits showed both of them to 

 be unduly toxic (pi. 42, figs. 3h and d). When diluted 50 per cent 

 with extracting fluid, however, the toxicity of both was greatly 

 reduced, though a red and indurated papule more than 5 mm. in 

 diameter, easily distinguishable from the control test and from the 

 tests on the normal rabbit, was still produced (pi. 42, figs. 1 and 2). 

 The difference in the size of the papule produced by L. tropica and 

 by L. infa^itum persisted. The cause of this difference is, as yet, 

 obscure. 



The results of these tests are as shown in table 2. 



DISCUSSION 



It is probable that the immunization of rabbits to Lrishmania 

 produces in them the condition classified by Coca (1923) as hyper- 

 sensitiveness of infection. Hypersensitivene.ss to derivatives of bac- 

 teria has been demonstrated by a number of investigators through 

 the use of the intradermal test. Von Pirquet (1911) showed that 

 the intradermal injection of vaccine lymph produces, in previously 

 vaccinated persons, marked papules after 48 hours. Force and 

 Stevens (1917) have described in detail the papule produced by the 

 intradermal injection of typhoidin in typhoid immune rabbits. The 

 intradermal tuberculin reaction in both man and animals is so gen- 

 erally known that a resume of the literature is scarcely necessai-y. 

 Recently Fairley (1923) found that the Casoni intradermal reaction 

 gave positive results in 57.9 per cent of patients with proved hydatid 

 infestation. This intradermal reaction is not constant in all cases 

 giving positive complement fixation or precipitin reactions; in ca.ses 

 of ruptured cysts, this is due to the desensitization of the patient. 

 Lanfranchi and Sani (1921) produced, with antigens prepared from 

 Trypanosoma brucci, an ophthalmic reaction which persisted 36 hours 



