History of T. gambiense and T. rhodesiense in Rats, etc. 213 
times diluted with a little physiological salt solution, or with a little isotonic 
sodium citrate solution. Methylene blue was sometimes used for entra vitam 
staining. 
Wet preparations of the parasite were made on cover slips after fixation 
with osmic acid vapour or corrosive acetic alcohol. The chief stains used 
were iron hematoxylin and those of Giemsa and Romanowsky. 
Dry smears were employed for rough work. 
In animals killed at certain stages of infection, the various internal organs 
were carefully examined both in fresh preparations and stained smears. | 
The enumerative methods used were those recently employed by R. Ross 
and D. Thomson and used by various workers in Liverpool, being an 
elaboration of R. Ross’s thick-film method made with measured quantities 
of blood (1 cubic millimetre divided into quarters). The films were 
dehzemoglobinised, fixed in absolute alcohol, and stained by the Romanowsky 
method. 
Resumé of Previous Work on Latent Bodies of Trypanosomes. 
The various flagellate forms of Trypanosoma gambiense have been so often 
described by many competent workers that it is needless to discuss them 
further in detail. Suffice it to say that long, thin trypanosomes may occur, 
especially at the beginning of infection in rats and guinea-pigs, and shorter, 
stout or stumpy forms later. Trypanosomes intermediate in character also 
are found. 
The so-called rounded, latent or encysted forms, which are non-flagellate, 
must be discussed in greater detail. Marked attention to these non-flagellate 
forms of trypanosome was first drawn by Moore and Breinl (1907-8) in 
mammalian trypanosomes, though Dutton saw rounded forms of an Amphibian 
trypanosome on the Congo in 1903-5. Moore and Breinl (1907), working 
on stained materiai, stated that latent forms occurred in the internal organs 
especially during the periods when the flagellates were decreasing or absent 
from the peripheral blood of the host. These authors give a curve showing 
the variations in the numbers of 7. gambiense in infected rats; they do not, 
however, give any numerical data in support of the graph. A few other 
workers have mentioned rounded bodies in connection with trypanosomes, 
among whom Hindle (1909) may be noted. The significance of the latent 
bodies is still a disputed point, and it was recently stated in a review that 
more evidence was required to show that they “constitute part of a life-cycle 
in the Vertebrate host.’* 
In the present paper the general statements of Moore and Breinl, 
regarding forms of 7’. yambiense in the internal organs of rats, are shown to 
* Sleeping Sickness Bureau, Bulletin No. 15 (March, 1910), p. 102. 
