UGANDA'S SCOURGE 29 



rats, guinea-pigs, and rabbits by Drs. Fantham and 

 J. G. Thomson. Dr. Fantham also explained the 

 periodicity. 



When a Glossina palpalis bites a man, only a few 

 trypanosomes can pass into the human circulation 

 as a result of the bite. For the perpetuation of 

 them, increase was necessary, and consequently 

 rapid multiplication of the parasites by longitudinal 

 division occurred. This continued for some time, 

 and the first crest of the curve was reached. As a 

 result partly of the reaction of the host on the 

 parasites, and also of the over-vigorous multiplication 

 of the parasites themselves, some of the trypano- 

 somes die and their bodies degenerate. Others show 

 resistance, retreat to the internal organs, and there, 

 withdrawn from the general circulation, become 

 latent bodies. Consequent on these two causes, the 

 number of trypanosomes in the peripheral blood 

 decreases to a minimum. With the diminution of 

 resistance on the part of the man or other infected 

 vertebrate, the re-formation of the flagellate trypano- 

 somes commences, and is followed by division. 

 Again, an increase in the number of flagellates in 

 the peripheral blood occurs, and the curve plotted 

 shows a gradual rise, until at the period of the 

 seventh day in man the maximum is reached, only 

 to be followed by a gradual decrease in numbers, 

 and corresponding descent of the curve as the 

 trypanosomes gradually disappear from the peri- 

 pheral circulation. Thus does the careful observa- 

 tion of morphology elucidate the puzzling periodicity 

 in numbers obtained by the enumerative methods. 



