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125
The fall in rat Plague of the 14th and 15th weeks corresponds to a heavy drop in human Plague during the 15th week. The sudden rise again in the 16th week of rat Plague accompanies a corresponding rise in the human curve but the sudden fall again in the rat curve for the 17th week is not answered by a fall in the human curve.
It is interesting to note that whereas the rat plague curve continues to ascend reaching its maximun at the 24th week, yet the human curve reaches its maximum in the 21st week, and after that, with the exception of a slight rise in the 23rd week, very rapidly falls so that by the 26th week the human curve is lower than it was in the 13th week although the rat curve is nearly 50 per cent. higher than it was at the 13th week.
From the behaviour of the curves at the rise of the epidemic one would have expected to see the human curve keep up with the continued high level of the rat curve during the 23rd to 26th weeks inclusive, but the fact that this is not the case must not be ignored. The epidemic of Plague amongst rats evidently follows very much the same curve as does the human epidemic but it seems to begin earlier and to endure longer as though there were some factor or factors in the shaping of the epidemic which affected the rats earlier, and of which the influence passed off later from these animals than in the case of human beings.
It is highly probable that a great number of the rats collected by the rat- catchers have been imported into the City, but as the price (5 cents) per head has been the same throughout the year there has been no special reason for a larger number of rats being collected in any one week more than another. Although the figures for the percentages of rats infected with Plague may not represent the numbers of such rats properly belonging to the City yet it is probable that the general trend of the rat curve is correct.
The following Table will shew that, while the number of rats collected weekly in the Colony remained fairly constant, yet the percentage of infected rats gradually increased up to the middle of June.
Table of Weekly Rat and Human Plague.
Week ending
NO. OF RATS
RATS
NO. OF CASES OF
%.
COLLECTED.
INFECTED.
HUMAN PLAGUE.
January
5
2,407
15
0.6
0
12
2,715
19
0.7
0
59
19
3,407
19
0.55
1
26
3.913
38
0.9
3
12
February 2
2,763
29
1.05
1
9
3,150
57
1,8
13
"
16
3,646
69
1.8
2
23
4,113
69
1.6
4
March
4,317
89
2.06
15
3,900
112
2.8
IS
16
4,046
104
2.5
19
23
3,271
155
4.7
27
30
3,568
183
5.1
38
April
6
3,153
141
4.4
58
13
3,875
146
3.7
24
20
3,392
190
5.6
62
11
27
19
3,620
144
3.9
99
May
4
3,193
177
5.5
102
11
3,691
227
6.1
80
18
3,671
211
5.7
117
}}
25
3,426
206
6.0
157
""
June
1
2,974
211
7.0
120
8
2,552
225
8.8
133
21
15
2,382
218
9.1
86
""
22
2,245
171
7.6
لان
29
2,015
162
8.0
32
July
J
6
1,781
57
3.2
34
13
19
1,674
32
1.9
22
20
1,868
37
1.9
14
27
1,990
43
2.1
14