1901-2.] Plague Research Laboratory of Government of India. 130 
Males 
Females 
21 not inoculated had 14 cases with 7 deaths. 
6 inoculated ,, 0 ,, 0 ,, 
1 1 not inoculated had 5 cases with 5 deaths. 
15 inoculated ,, 1 „ 0 ,, 
The above particulars, carefully got together by painstaking 
enquiry, prove 
(a) That the infection was localised in the chawl. 
( b ) That all the inhabitants were living under precisely the same 
conditions, with the single exception that some were inocu- 
lated and others not. 
(c) That the lessened incidence of plague in the inoculated was 
due solely to the effect of the material injected. 
These two demonstrations, which are accurate to a high degree,, 
prove unquestionably the two propositions formulated above 
(p. 128), and which may be again restated with the added weight 
of the words of the Indian Plague Commission.* 
“ 1. Inoculation sensibly diminishes the incidence of plague 
attacks on the inoculated population, but the protection which is 
afforded against attacks is not absolute.” 
“ 2. Inoculation diminishes the death-rate among the inoculated 
population. This is due not only to the fact that the rate of 
attack is diminished, but also to the fact that the fatality of attacks 
is diminished.” 
Two further questions now arise, viz. : — 
(a) Is the plague vaccine harmful when applied to those in the 
incubation stage of the disease ? and 
(b) When does protection begin to be effective, and how long: 
does it last ? 
As regards the first of these queries, we find Calmette asserting, 
before the International Congress of Hygiene and Demography at 
Paris, in September 1900, that “a person in the period of in- 
cubation for a slight attack of plague would find the disease 
considerably aggravated if he submitted during this period to a 
preventive inoculation of Haffkine’s vaccine. The case would 
almost certainly end fatally.” f Some months later the same- 
* Report of the Indian Plague Commission, vol. v. p. 262. 
t Abstract in Brit. Med. Journal of 27th October 1900. 
