312 
Trypanosoma lewisi 
TABLE IY. 
Showing 'prevalence of trypanosome infections in M. decumanus (abstracted 
from Lingard’s Reports) and of A die’s Leucocytozoon in M. rattus ( ab¬ 
stracted from Plague Commission's Reports). 
Percentage of M. decumanus infected 
with trypanosomes 
Percentage of M. rattus infected 
with leucocytozoon 
May 1894 
31-2 
December 1905 
16-8 
June 
27 '5 
January 1906 
14-6 
July 
46-7 
February 
7-1 
August 
43-0 
March 
4-1 
September 
46-3 
April 
0-7 
October 
40-4 
May 
5-4 
November 
37-5 
June 
22-4 
December 
34 1 
July 
21-7 
January 1895 
27-5 
August 
21-6 
February 
26-6 
September 
19-2 
March . . 
241 
October 
16-7 
April 
23-4 
November 
15-8 
question of the 
correlation of the prevalence of the 
infection with 
the seasonal prevalence of the ectoparasites of rats. 
The insects which infest the Bombay rats are fleas ( Loemopsylla 
cheopis , Rothsch.) and lice. With regard to the prevalence of rat 
fleas in Bombay the extensive data collected and published by the 
Plague Research Commission (1908) are happily available for com¬ 
parison. It seems scarcely necessary to point out that rat fleas are 
very abundant on the rats in Bombay. The Commission found 
that the average number of fleas per rat taken from M. rattus during 
a year’s investigation was 3'7, while the average number per rat 
in M. decumanus was 8'5. They further determined that there is 
a definite seasonal prevalence of rat fleas in Bombay. The curves 
of rat flea prevalence are reproduced from the Commission’s reports 
in Chart III, from which it will be seen that the highest point 
of the curve of fleas taken from ill. rattus falls in March and April and 
corresponds to an average per rat for these months of 5‘2 fleas, while 
the lowest point is found in November, corresponding with an average 
of 2'5 fleas per rat. The highest point in the M. decumanus curve 
corresponds to an average of 14 fleas per rat in April and the lowest 
point to an average of 4 - 2 per rat in September. When a comparison 
is instituted between the rat flea curves of prevalence and the curves 
representing the prevalence of trypanosomes it is at once obvious that 
