450 
somewhat irregular series of well-marked periods, the kind of 
oscillation produced being indicated in the chart given on page 44). 
When an animal has been previously infected, it has been found that 
even at a period when no parasites can be detected in the blood, the 
blood is nevertheless capable of infecting other animals by sub¬ 
inoculation. 
As is already well known, Trypanosoma gambicnse can be 
transmitted from animal to animal by the bites of flies; but the 
observations of Bruce* and others have shown that if more than 
48 hours elapse after the flies have fed on an infected animal 
subsequent bites produce no infection. The observations of Dutton, 
1 odd and Haningtonf made on the Congo, show further that it is 
often extremely difficult to infect at all with flies, and the authors sum 
up the position in respect to this matter in the following paragraph 
“ ,T e ' eheVe eithCr ’ ^ That someth ing is wrong in the way m 
«ml C t G/ °* S * na * al * alis has ^en used in these experiments'or, 
„ W l hat Trypanosoma gambtense can be conveyed by some other 
means than by it.” ' 
o far, then from it being established that Sleeping Sickness is 
orma y spread among the African population by the bites of 
thfT*' aI ° ne ' U W ° U,d hSem that the most «*ent work on 
n he nit "f**" ^ P ° SSib '> the Action through fl.es is 
Smkness s 6 °J "" T ' “ d tha ‘ the means ^ which Sleeping 
mtermr ha t S ; m ? e a manner ‘ n W ’ lich " d °“ * P rL in the Afiean 
interior, has yet to be discovered. 
ryP r 0Smna in „u Blood of an InfccUi Ann 
vary i “ “l^^TT" " tad 
represented in figs. , B /'. ,, fr ° m f ° rms smalIer than 1,10 
gradually to the f j ’’ we llia y select a series increasii 
r™ •*—«- *,» 
FWd, ,, does net ^ , b) ° to d «“ '' 
trimorphism, corresponding to the s ^ dun0rphlS ”’' ‘ 
b tile so-called male, female, an 
* Bruce, loc. cit. 
t Dutton, Todd and Hani„g, on , l oc . cit 
