Manuel d'entomologie médicale . especly la structure du stade sang-habitant. Les trypanosomes sont allongés, habituellement des protozoaires à point flagré (fig. 136) dans laquelle le flagellum de thesingle, le rentsous le corps, forme la limite extérieure d'une membrane ondulée délicate. Il se trouve près d'une extrémité de l'organisme à partir d'une minute de genre centrosome qui est connu sous le nom de blepheroplast, et à l'extrémité opposée extendspour une distance plus ou moins grande comme flagellum libre. L'enfermer, orclose à côté du blepheroplast est le petit kinetonucléus. Le noyau principal, rond ou ovale, est situé près du cen

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Handbook of medical entomology . efly the structureof the blood-inhabitingstage. The trypanosomes areelongated, usually point-ed, flagellated protozoa(fig. 136) in which thesingle flagellum, bentunder the body, forms theouter limit of a delicate undulating membrane. It arises nearone end of the organism from a minute centrosome-like bodywhich is known as the blepheroplast, and at the opposite end extendsfor a greater or less distance as a free flagellum. Enclosing, orclose beside the blepheroplast is the small kinetonucleus. Theprincipal nucleus, round or oval in form, is situated near the centerof the body. Asexual reproductions occiu-s in this stage, by longi-tudinal fission, the nucleus and the blepheroplast dividing independ-ently of one another. From the blepheroplast of one of the daughtercells a new flagellum is formed. Among the pathogenic species are to be found the causativeorganisms of some of the most serious diseases of domestic animalsand even of man. It is probable that these pathogenic species secrete. 136. Trypanosomc brucei. After Bruce. Fleas and Lice as Carriers of Trypanosoma lewisi 213 a specific poison. The majority of them are tropical in distri-bution. Though we are concerned especially with the species which infestman, we shall first consider two of the trypanosomes of lower animals, known long before an} of those of man had been found. Fleas and Lice as Carriers of Trypanosoma lewisi.—Trypanosomalewisi, the first mammalian trypanosomc known, is to be found in theblood of wild rats. Like its host, it appears to be cosmopolitan indistribution, having been reported from several localities in theUnited States, Brazil, Argentine, England, Germany, France, Italy, Russia, Asia and Africa. This species is usually regarded as non-pathogenic, but in experi-mental work, especially with white rats, heavy infestations oftenresult fatally, and naturally infested specimens sometimes showevidence of injury. Rats which have been infested exhibit at leastte

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