812 THE FLAGELLATA 



centrosome in which the flagellum terminates [cf. morphology of T. 

 gambiense, p. 818]. 



Multiplication takes place by binary longitudinal fission (Laveran and 

 Mesnil) ; this commences with division of the centrosome, and is soon followed 

 by division of the flagellum, nucleus and protoplasm (fig. 393). 



Involution forms. Under unfavourable conditions involution forms make their 

 appearance : the trypanosomes become stumpy, roll up into balls and form small 

 agglomerations. These forms were taken by Bradford and Pliinmer to represent 

 stages of multiplication. 



When a trypanosome dies the cytoplasm disappears first, then the nucleus, and 

 finally only the flagellum and centrosome remain. 



Cultures. Novy and MacNeal obtained cultures of Tr. brucei on their 

 blood-agar medium. Cultures often remain sterile so that it is advisable 

 to sow a large number of tubes to ensure a successful result. Growth takes 

 place between 25 and 34 C., but the higher the temperature the more 

 quickly do the parasites die : at the temperature of the laboratory a culture 

 may remain alive for 45 days. Novy and MacNeal have succeeded in sub- 

 cultivating to the fourteenth generation. 



Cultures grown at 25 C. are seldom as virulent as trypanosomes from 

 the blood and only kill rats and mice in 7-10 days instead of in 3-5 : at 

 34 C. they rapidly lose their virulence. 



In cultures the trypanosomes are generally arranged either in pairs con- 

 nected by their aflagellar ends, or in rosette-shaped colonies consisting of 

 10 to 20 individuals, the flagella appearing to be situated at the periphery 

 of the rosette. 



Agglomeration. Outside the body the trypanosomes in the blood of 

 infected animals soon exhibit apart from the involution forms which have 

 been described the phenomena of agglomeration (Laveran and Mesnil, 

 Martini). Forms similar to those which have already been described 

 as occurring in cultures association of two parasites and rosette-forma- 

 tion are seen. The agglomerated masses may break up after a variable 

 time. 



Agglomeration is hastened by the addition of serum from a dog, horse, sheep, pig, 

 monkey, etc. Human serum exhibits no agglomerating action, and the serum of 

 an immunized goat has no more agglomerating action than a normal goat's serum. 

 The serum of a cow, immunized by Nocard, was highly agglomerating but had no 

 trypanicidal properties. 



Experimental inoculation. Trypanosoma brucei will readily infect most of 

 the mammalia. Man however is [thought to be] immune. 



Inoculation is followed by infection whether the blood of the infected animal 

 (which is the material generally used) be inoculated sub-cutaneously, intra- 

 venously, or intra-peritoneally. 



Infected blood, if kept free from contamination, loses its virulence outside the 

 body in a few days whether it be kept in the ice chest or at laboratory temperature 

 (Laveran). Desiccation also renders it harmless. 



The incubation period varies for a given species both with the number of 

 parasites inoculated and with the condition of the parasites. The disease is 

 always acute and fatal in mice, rats, dogs and monkeys ; subacute in rabbits, 

 guinea-pigs, horses, asses and pigs ; and chronic in cattle, sheep and goats : 

 these last may recover from infection. Grothusen and Martini have suc- 

 ceeded in infecting a zebra : this fact is in contradiction to the immunity 

 which the zebra seems to possess in nature. 



The most constant symptoms in all animals are oedema, fever, anaemia, 

 wasting and paralyses. In rats and mice the parasites multiply until at 



