6 
OhservatioRS on British Rat-Jieas 
say exactly what the clearly-marked seasonal variation in the average 
number of fleas per rat was due to, whether to the temperature, 
humidityh or to a combination of these. We think the temperature 
the more important factor, but this point could only be settled by more 
extended observations. 
For the purpose of comparison with our results we have charted the 
average number of fleas per rat found by Martin and Kowland during 
November and December, 1910, in the same part of Suffolk, when the 
temperature and humidity had declined to a still lower point than they 
had in October, 1911, during our observations. 
TABLE I. 
No. 
District 
Comprising i 
No. 
of rats 
examined 
Average 
fleas per 
rat 
Plague 
Preseut{-r) 
Ab.sent (-) 
1 
Nacton 
Nacton Parish 
22 
6-5 
- 
2 
Tuddenham ... 
Swilland, Witnesham, Culpho, Tudden¬ 
39 
6-0 
- 
3 
North Essex ... 
ham, Akenham, Claydon. 
Lawford, Ardleigh, Dedham, Langham, 
40 
5-8 
4 
Tattingstone ... 
Boxted, Great Horksley. 
Tattingstone, Brantham, Wherstead, 
54 
5-3 
5 
Bawdsey 
Bel stead. 
Bawdsey, Alderton... 
30 
5'3 
+ 
6 
Hollesley 
Hollesley, Shottisham, Boyton 
32 
5-1 
- 
7 
Sutton 
Sutton Parish 
22 
5’0 
i- 
8 
Freston-Shotiey 
Freston, Holbrook, Harkstead, Shotley, 
35 
4-8 
+ 
9 
Kushmere 
Woolverstone, Chelmondistone. 
Bushmere Parish ... 
49 
4-3 
10 
Bramford 
Bramford, Hintlesham, Holton, 
45 
3-8 
- 
11 
Kesgrave 
Sproughton, Great and Little Wen- 
ham, Capel St Mary 
Brightwell, Kesgrave, Martlesham 
69 
3-7 
12 
Playford 
Playford Parish 
45 
3-6 
- 
13 
Felixstowe 
Walton, Felixstowe... 
45 
3-2 
- 
14 
Framlingham... 
Kendham, Swefling, Parham, Easton, 
100 
3-2 
- 
15 
Newbourne 
Earl-Soham. 
Foxhall, Newbourne, Bucklesham, Pur- 
34 
2-8 
4- 
16 
Bentley 
dis Farm, Waldringfield. 
Bentley, Washbrook, Copdock, East 
45 
2-7 
j- 
17 
West Suffolk ... 
Bergholt. 
Boxford, Assington... 
11 
2-6 
18 
Melton 
Melton, Hasketon, Ufford 
47 
1-9 
- 
19 
Ipswich 
Ipswich Borough 
22 
1-6 
20 
Boulge 
Boulge, Bredfield ... 
30 
0-6 
- 
’ The Indian Plague Commission, whilst working at Belgaum, India, found that 
humidity, within certain limits of temxjerature, played some part in the increase of fleas. 
This increase occurred a little time after the increase of humidity. 
