16.1 Haughwout and Youngberg: Trypanosomiasis 83 
length upon this appearance as representing any definite develop- 
mental phase of this particular trypanosome, although it might 
well be that very thing. 
There is an interesting resemblance between these individuals 
and those figured by Kofoid and McCulloch ^ in plate 15 of their 
paper on Trypanosoma triatomae. Their figures, however, are 
of forms found in the digestive tract of the hemipteran Triatoma 
protracta and their paper does not deal with the forms found 
in the blood of the vertebrate host. 
It must be borne in mind that certain factors were present in 
the carabao from which the trypanosomes were obtained that 
might have altered the morphology of the parasites. It is barely 
possible that the antirinderpest treatment and the injection of 
virulent blood might have exerted some influence on the trypa- 
nosomes. It must also be recalled that the blood from which 
our slides were prepared was taken from the animal after death. 
In view of this, it has seemed to us possible that the appearances 
we have noted may have been the expression of a more or less 
abortive effort on the part of the trypanosome to develop a 
crithidial stage similar to that it might be expected to assume 
in culture or in its invertebrate host. This might be due to the 
lowering of the temperature and the initiation in the blood of 
conditions approaching those found in an artificial culture. 
Measurements were made (by the method of Stephens) of 
one hundred individuals selected at random from the best- 
preserved and stained trypanosomes we could find on the slides. 
We have plotted the size distribution of these trypanosomes in 
fig. 2. 
In general, we believe the trypanosome described by us more 
closely resembles Trypanosoma theileri than it does any of the 
larger trypanosomes we have had under consideration. It ap- 
proaches the descriptions of Theiler(9) and of Laveran(3, 4) 
more closely than it does the current descriptions of Trypanosoma 
americanum. Martini’s description of his trypanosome gives 
us no clue whatever. Flies of the genus Hippobosca, which are 
credited with being the vectors of T. theileri, axe frequently found 
in the Philippine Islands. Musgrave and Clegg (7) report the 
infection of Philippine carabaos with Trypanosoma evansi, a 
fact we have many times confirmed, but our parasite certainly 
’ Kofoid, C. A., and McCulloch, Irene, On Trypanosoma triatomae, a 
new flagellate from a Hemipteran bug from the nests of the wood rat 
Neotoma fuscipes, Univ. Calif. Pub. in Zool. 16 (1916) 113. 
