CHAPTER XI 
DISEASES CAUSED BY PROTOZOA 
GENUS 'TRYPANOSOMA 
Classification of trypanosoma. The trypanosomata belong to the 
protozoa, but their species diagnosis is not satisfactorily determined. 
A number of classifications of these organisms have been proposed. 
The one suggested by Salmon and Stiles is appended. 
Protozoa, class Mastigophora, subclass Flagellata, order Monadida, 
family Trypanosomidae, genus Trypanosoma Gruby. 
According to Stiles the family contains at present two genera, 
which are distinguished as follows: 
1. One flagellum present, extending from the centrosome along the undulating 
membrane and becoming free at the anterior extremity.......... Trypanosoma 
2. Two flagella, one extending anteriorly, the other posteriorly... .Trypanoplasma 
Generic diagnosis of Trypanosoma. “Body fusiform, presenting a lateral, longitu- 
dinal, undulating membrane, the thickened border of which terminates posteriorly, in 
the posterior half of the body in a ‘centrosome,’ and is prolonged anteriorly in a free 
major flagellum; nucleus generally anterior; there is a tendency to agglomeration by 
the posterior extremity; divisions longitudinal and unequal. Parasitic in the blood of 
vertebrates.” 
In order that a somewhat definite idea of the structure of these 
organisms may be obtained the specific characters of Tr. Lewisi are 
quoted: 
Trypanosoma: “8 to 10u long, 2 to 32 broad, 24 to 34u, long by 1 to 444 broad(Laveran 
and Mesnil, 1901); a very refringent granule (near centrosome) in place of which a 
clear vacuole is seen in stained preparations. Animalcules exceedingly minute, alter- 
nate and vermicular under normal conditions, but highly polymorphic and capable of 
assuming a variety of contours; flagellum single, terminal, two or three times the length 
of the extended body. No contractible vesicle . . .as yet detected. Habitat, 
blood of the rat and hamster.” 
Schaudinn distinguished several genera* of the Trypanosomide and 
his classification has been adopted by many writers. 
*The genus Trypanosoma: having an undulating membrane and one flagellum. 
The genus Trypanoplasma: having in addition to an undulating membrane and 
an anterior flagellum, a second free flagellum inserted into the posterior part of the body. 
The genus Herpetomonas: having a free flagellum but no undulating membrane. 
The genus Spirocheta: elongated, sinuous organisms having an undulating mem- 
brane, but no flagellum. 
The genus Treponema: elongated, sinuous organisms having a short flagellum at 
each end but no undulatory membrane. 
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