TRYPANOSOMES, TRYPANOSOMIASIS, AND SLEEPING SICKNESS 47 
have included rats, mice, guinea-pigs, and rabbits. This parasite has naturally a 
stumpy form and possesses the peculiarity of a marked tendency to agglutinate in 
animals near death ; this is especially the case in moribund rats and mice. After 
inoculation of the culture tubes very little is noted for the first three to four days, 
and the parasites are usually gathered together in large clumps or several of them are 
agglutinated side by side or by their anterior ends. The motility is not altered, the 
form is normal and the parasite stains as usual. Cultivated in the room or at 22° C. 
changes occur after the fifth day, especially in the tubes incubated at 22° C. The 
parasites become slower and many show granules. Numerous globular and distorted 
forms are seen. About the seventh to eleventh days the majority are either motion- 
less or dead. However some very acutely rounded or oval forms, pear-shaped and 
twice as broad and about half as long as the normal ones, are seen. These latter 
often recall the ' tadpole ' shape, and they may become more rounded. Coincident 
with these changes larger forms appear, which to a certain extent resemble in size and 
shape cercomonads. The motility of both these forms is remarkable when compared 
to the ordinary motion of the parasite ; it is very striking to observe them as they 
whirl into a field and circle round, often lashing out and going to the side of or 
leaving the field. Their motion is however, usually circumscribed to the one field. 
Such forms when stained show a badly staining granular protoplasm, a very small 
macronucleus and micronucleus. Usually the body of the rounded forms contains 
small chromatin bodies. The flagellum is thin and only faintly stained, the 
undulating membrane is hard to make out. In order to stain these forms, longer 
staining is necessary than with normal trypanosomes. If now, cultures containing 
these bodies be transplanted, very few of them will survive. Cultures containing 
these forms are non-infective to animals. 
Cultures at 22 0 C. containing normal-looking trypanosomes have proved infective 
to animals as late as the twenty-third day, but only when injected in large amounts. 
By sub-inoculations of the cultures of the very active but degenerated forms, it may 
be possible to keep the parasites alive to the thirty-sixth day. A second generation 
tube which had been inoculated with a small piece of the surface of a blood agar flask 
which had been covered with clotted blood, showed two trypanosomes almost dead, 
but faintly moving on the seventy-sixth day. This tube was sub-inoculated from 
a 22 0 C. flask on the nineteenth day and left sealed up from the thirty-second day. 
No other parasites than these two could be found. 
Summary 
1. The parasite T. equiperdum in blood agar tubes is capable of infecting a pup 
up to the seventeenth day, when the tubes are kept at 2 2° C. 
2. The parasite of T. equinum is capable of infecting a rat twenty days after 
the inoculation of the tube. There appears to be an actual growth taking place. 
