46 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
occur. The flagellum is usually shorter, and it and the undulating membrane when 
stained appear thinner. The motility of some of the forms is accentuated, but 
usually the motion is markedly lessened. Many parasites are globular and show 
whitish areas, apparently vacuoles, in the body, and these sometimes encroach on the 
macronucleus. The motility of these forms is nearly always lessened. The 
trypanosomes usually occur singly or in two, three or four to a group, sometimes 
clumps of twenty to thirty will be found, the flagella facing outwards ; these clumps 
are not composed solely of parasites, but consist of a mixture of blood cells, fibrin, 
and trypanosomes. Rarely after the twenty-fifth day have normal looking organisms 
been seen, though at this time there may be found dead trypanosomes with perfectly 
formed outlines and flagella. If from the sixteenth day onwards attempts be made 
to transplant the motile trypanosomes into fresh media the majority of the tubes will 
be failures. A few, however, may survive, and in these, after a few days, the 
trypanosomes will appear to lengthen out and become still more normal looking. 
The motility is normal, but unfortunately no duplication forms will be seen. No 
evidences of actual growth occur, and usually by the twenty-fifth to fortieth day from 
the first generation the organisms will be found dead. Such cultures naturally do 
not infect animals even when the whole culture is used to infect one animal. On 
three occasions tubes which on the twelfth to seventeenth days had looked hopeless, 
with the degenerating parasites increasing each day, have on the addition of fresh 
culture fluid from another tube appeared rejuvenated ; some of the parasites appearing 
to lose their dark granules and to become less stumpy. Twice the contents of such 
tubes have been poured into other tubes, and the parasites have continued motile up 
to the forty-third day. The parasites of a first generation tube which behaved in 
this manner were transplanted into another tube, and were alive, though badly 
degenerated, up to the fifty-sixth day. They were once more transplanted, but twelve 
days later were all dead. The original tube had contained motile trypanosomes up 
to the forty-seventh day. 
Various strains of T. gambiense have been used. Some of the cultures were 
inoculated with blood in which the short flagellated and vacuolated form, though 
associated with the longer form of the parasite, predominated. It has been noticed 
later on in such cultures that sometimes more vacuolated short forms remained or 
vice-versa. This, though it may not be definite, goes to refute the idea which some 
investigators have put forward that the short vacuolated form is typical of the 
parasite found in sleeping sickness cases. With the very virulent strain ' E ' some 
attempts have been made to cultivate the parasites. No living trypanosomes have 
been found after the nineteenth day. These cultures were non-infective for animals. 
7. dimorphon. — A great deal of work has been done with this parasite. Tubes 
of culture media of the same proportions as in the experiments with T. gambiense 
have been used and the animals from which the inoculating material has been taken 
