ZOOLOGY: R. ERDMANN 505 
For one strain of trypanosomes, herein designated as 'M,' with which 
the experiments were made I am indebted to Prof. F. G. Novy of the 
University of Michigan. It is the same Nagana material which was 
used by Kanthack, Durham and Blandford, and Laveran and Mesnil 
for so many years. A second strain, 'R', was secured from Dr. W. Brown 
of the Rockefeller Institute. However, since both strains showed 
the same changes in the plasma medium, I shall confine myself chiefly 
to a description of strain M. Also, in describing the morphology of the 
forms studied, I shall refer, in this paper, to the larger nucleus merely 
as 'nucleus,' and the smaller nucleus as blepharoplast, thus avoiding any 
discussion as to the fundamental origin or theoretical significance of 
these structures. 
It will be necessary to keep in mind some general observations con- 
cerning the growth of this well known strain (M) in the rat, in order to 
interpret some of the phenomena observed in the plasma. The period 
in which the strain kills the rat after infection is generahy three or four 
days in length, when 2 cc. of Ringer's solution, with six drops of blood 
taken from an animal shortly before its death, is used. When one 
trypanosome is used for inoculation, the lethal period lasts five days.^^ 
At the end of this period, shortly before death, there appear generally 
only those forms which have a well marked nucleus and are known as 
'Schmalformen.' Schilling!^ mentions them at this period, and Oehler^^ 
considers them as 'Wucherformen.' Observed with dark-field illumi- 
nation, 72 hours after infection, these animals appear as shown in figure 1, 
f and g. Text figure 1, d and e, represents trypanosomes 62 hours after 
inoculation. These animals are larger because they are probably not 
in such a rapid period of multipHcation as animals f and g. Forty-eight 
hours after inoculation animals of the type figured in figure 1, b and c, 
can be discovered. These forms are the so-called 'Breitformen,' which 
are distinguished by their wealth of granules. Since Kiihn and von 
Schuckmann^^ rarely observed forms filled with granules it would seem 
that they must have taken the material for their excellent cytological 
studies shortly before the death of the infected animal. In strain M, 
after 48 hours infection, broad forms with granules prevailed, but forms 
without granules could also be detected. Trypanosomes which are 
about to die often show a granular appearance, but those observed in 
plasma, and figured in figure 1, a, b and c, w^ere living and moving in the 
manner characteristic of Trypanosoma brucei. Thirty-six hours after 
subcutaneous inoculation the trypanosomes in the peripheral blood are 
very scarce. An example of an animal from the blood at this period 
is shown in text figure 1 a. The characteristic shape of the trypano- 
