210 REVIEW — TROPICAL MEDICINE, ETC. 



Tsetse Flies Minchin' reported fully on the anatomy of G.palpaUs, in a woU-illustrated paper, followed 



— cmitiniicd by a proliniiuary article on the relation of this fly to T. gamhiense. This work is now so 

 well known to all interested in the subject that there is little need to discuss it in detail. 

 Suffice to say that Minchin and his fellow-observers. Gray and TuUoch decided that the 

 trypanosomes found in freshly-caught tsetse flies, and named by Novy T. grai/i and 

 T. tidlochii, have nothing to do with sleeping sickness, and are not developmental stages of 

 T. gamhiense. They were not able to determine on what vertebrate host, if any, these 

 trypanosomes are parasitic, but indicate two possible sources for them (a) some of the 

 numerous animals, water birds, crocodiles, hippopotami, etc., upon which the fly feeds; 

 (h) these trypanosomes may be parasites of the fly itself, like the Herpi'iinnonas of the 

 domestic fly, or, one may add, of the Nile Seroot. 



Their observations showed that T. gamhiense itself actually does die out in the tsetse fly 

 after the third day. It was only found in the mid-gut of the fly. 



In the same publication, Minchin describes the occurrence of encystation in T. grai/i, the 

 form produced resembling what is found in Rerpetotimnas infections. Dealing with the 

 significance of this process, he says : — 



It seems to me in the highest degree improbable, indeed, I may say impossible, that a tsetse-fly would ever 

 infect itself by sucking up cysts dropped by another fly, or that a parasite which had to depend on this method or 

 dissemination could maintain its existence in the tsetse fly. The only possible destiny I can imagine for these 

 cysts is to be swallowed accidentally by some vertebrate, the (as yet unknown) host of Trypanosoma r/ratji, in 

 order to germinate in its digestive tract, to pass thence into the blood, and to be taken up again with the blood by 

 the tsetse fly. A cycle of this type is as yet unknown, but there are abundant analogies for all parts of it. In 

 the first place, it is a common thing for animals to have protozoan parasites in the gut, which they take up in the 

 encysted condition after they have been dropped by another individual. Without multiplying instances 

 unnecessarily, I may point out that Schaudinn proved the infection of Amceba coH to originate in this way, and 

 that it is a common human parasite in regions where sanitation has not advanced beyond the primitive condition 

 of epandaye par Urrr. In the second place, there are many instances among Sporozoa of cysts germinating in the 

 intestine and liberating motile forms which then pass through the wall of the gut into other organs of the body. 



In a former communication by my colleagues, Lieutenants Gray and Tulloeh, and myself, we were able to 

 confirm Brnce's results as to the existence of direct mechanical infection by means of the tsetse-fly, which if it 

 stabs its proboscis first into an infected animal and then soon after into a healthy one, can infect the latter. We 

 were not able to demonstrate, however, what I may term cyclical infection, which at present has not been shown 

 to exist. I suggest that there are two possible modes of cyclical infection, in the dissemination of protozoan blood- 

 parasites by biting insects generally. In one method, which I may term inoctihUirc, the parasite, after going 

 through developmental changes in the insect, passes back again into a second vertebrate host through the 

 proboscis, as in the case of malaria transmitted by a mosquito. In the other method, which I propose to term 

 coiitaiiiinativc, the parasite taken up by the biting insect, after going through developmental changes within its 

 gut, would pass out through the anus, and infect the vertebrate host by contaminating its food or drink. We have 

 all of us (I speak for my.self) been imbued hitherto with the idea that the cycle of the tryjjanosome in the tsetse 

 fly must he of the inoculative type, and have failed to find it. I wish to suggest strongly to those working on the 

 subject of trypanosome-infection the desirability of making experiments and observations to prove or disprove the 

 existence, in the insect which disseminates the parasite, of a life-cycle which results in a oontaminative infection 

 of the vertebrate host. 



His later work and conclusions^* have already received brief consideration under the 

 heading " Sleeping Sickness " {page 174). 



Tuberculosis. Such a wide subject cannot be fully discussed in a review like this, 

 but allusion will be made to such points as may be of interest and importance. 



Reference may be made to the absorption of tubercle bacilli by the skin. Nouri and 

 Osman^* found that if guinea pigs were shaved in the inguinal region and then rubbed with 

 absorbent cotton fouled with tuberculous sputum, the corresponding lymph glands enlarged 

 and became swollen in eight to fifteen days, and the animals died in thirty to fifty days. 

 This may explain to a certain extent the puzzling location of certain tubercular lesions 

 which are met with in Mohammedan and other countries where the art of shaving is some- 

 what crudely performed, the victim being shaved with water and a blunt razor and 

 the operator frequently adding his saliva as a soapy adjuvant ! 



As regards the presence of tubercle bacilli in the blood, Liidke,'' was able to isolate 

 the tubercle bacillus from the blood of consumptive patients by withdrawing 5 c.c. to 10 c.c. 



» Minchin, E. A. (February, 1907), " Beport on the Anatomy of the Tsetse Ply." Report Sleeping Sickness 

 Comm. Hoy. Sac, No. VIII. 



" Minc:hin, E. A. (March, 1908), "Investigations on the Development of Trypanosomes in Tsetse Plies and 

 other Diptera." Quarterly Journal of Microscopical Science, New Series, No. 206, Vol. LII, pt. 2. 



' Nouri, 0., and Osman, " Absorption of Tubercle Bacilli by freshly shaven skin." C. R. Soc. Biol., t. LIV., p. 308. 



< Liidke, H. (1906). Wiener. Klin. IVoch., No. 31, p. 949. 



* Article not consulted in the original. 



