CHAPTER XXXIX. 



TRYPANOSOMA. 



Subclass: Flagellata. 



Order: Protomonadina. 



Genus: Trypanosoma. 1 



The genus trypanosoma includes blood parasites of the vertebrates 

 distinguished by a somewhat long body more or less spirally twisted, 

 one to several flagella, an undulating membrane, one nucleus, and a 

 "flagellum root." The chief flagellum is directed forward, arising from 

 or near a small, more or less rounded structure, the "flagellum root " 

 (blepharoplast) , situated near the posterior end of the organism. The 

 nature of the "flagellum root" is still a matter of controversy. Some 

 consider it of the nature of a centrosome, others, of that of a micro- 

 nucleus. Schaudinn calls it the locomotor nucleus, and says it produces 

 undulatory membrane and flagella. If secondary flagella are present 

 they are generally directed backward. 



The undulating membrane extends along one side of the organism 

 from the "flagellum root" or near it to the anterior end of the parasite, 

 whence it continues as the free flagellum. It varies in size and fulness 

 according to age and species. 



The nucleus is situated anteriorly; it is granular, thick, and egg- 

 shaped, but varies somewhat in size and shape. The cytoplasm is homo- 

 geneous or granular, varying with age, environment, and possibly 

 species. The life cycle is not well known. Multiplication occurs through 

 longitudinal division; however, MacNeal states that the division is not 

 exactly longitudinal, but always more or less oblique in direction, and 

 that the flagellum does not divide, but a new one is formed in each 

 division. Conjugation has been observed in trypanosoma Brucei by 

 Plimmer and Bradford. 



Only a few of the many species of trypanosomes described are patho- 

 genic, and these principally for the lower animals, though recently the 

 organisms have several times been seen in human beings, accompanied 

 or not by pathological changes. Very recently Castellani stated that 

 the sleeping sickness of the negro is caused by a trypanosome. The 

 work of Schaudinn and of Novy and MacNeal make it evident that the 

 spirochsetes of recurrent fever and of geese belong to the trypanosomes. 



The first species of trypanosomes studied with any degree of fulness is 

 the comparatively non-pathogenic trypanosoma Lewisi, Kent. It is of 

 interest because of its similarity to the more pathogenic forms and because 

 of the ease with which it may be studied. It is parasitic in the blood of 



1 Special literature on trypanosoma : Laveran and Mesnil, Musgrave and Clegg, Novy and 

 MacNeal, and Schaudinn. 



