146 
E. A. MINCH1N AND H. M. WOODCOCK. 
smears of the bone-marrow ! The parasites were evidently 
extremely scanty; one of us, notwithstanding a fair amount 
of experience with Avian Trypanosomes, has never had 
another bird, in which these parasites were so rare in the bone- 
marrow. 
The incident of owl 19 emphasises the point that it is very 
difficult to be certain, from a living examination alone, that 
trypanosomes are absent from the bone-marrow. Small 
forms especially may be quite hidden by clumps of cells. 
The spreading out of a thin smear for a permanent prepara- 
tion helps to set free and disclose the parasites. 
The constant association 6f trypanosomes with one or more 
of the intra-cellular parasites, especially the Halteridium 
and Le ucocy toz oon, is very striking. In no case did we find 
trypanosomes in an owl which had not these two other forms 
also. Nevertheless, suggestive as this fact may be, we have 
been unable to obtain any evidence which would point to 
anything being concerned beyond coincident occurrence of 
these different types of parasite. Moreover, taking the other 
forms first, the coincidence is somewhat less marked. Thus, 
while five (possibly six) of the seven birds infected with Hal- 
teridium also had trypanosomes, in one certainly (No. 11) 
trypanosomes were not present; it is true that here the 
Halteridia were excessively scanty. Again, with regard to 
Leucocy tozoon, this intra-cellular parasite occurred in 
five birds in which no trypanosomes could be found. In 
the case of three of these, Nos. 11, 17, and 22, in which the 
Leucocy tozoon was either fairly frequent or else plentiful, 
good smears from the bone-marrow and also from the other 
organs (in the case of No. 22) have been well searched with 
negative result. 
As will be gathered from the table, Proteosoma occurred 
indiscriminately, either alone or together wdth one or more 
of the other parasites; while in owl 14, which had the other 
three forms, Proteosoma was absent. An interesting point 
of difference may be mentioned between Proteosoma on the 
one hand and Halteridium and Leucocy tozoon on the 
