880 SOME POINTS OF GENERAL INTEREST 
The pneumonic and septicaemic varieties of plague are 
extremely fatal forms. Unlike the bubonic form, pneumonic 
plague can easily be conveyed from one person to another 
without the intervention of fleas. In coughing, a pneumonic 
plague patient is showering his neighbourhood with millions 
of germs, and an attendant accidentally receiving some 
of this material on the mucous membrane of the mouth, or 
the conjunctiva of the eyes, may contract plague. 
The treatment of plague, so far, has not produced any 
specific. Most drugs have been tried, but with disappointing 
results. Anti-plague serum has also been disappointing in 
producing curative results. 
On the other hand, from a prophylactic point of view, we 
can produce a very considerable degree of active immunisation 
by the inoculation of cultures of plague bacilli or its products. 
The chief of these is Haffkine’s Vaccine, of which all of you 
have personal acquaintance. Plague bacilli are prepared in 
broth cultures, in the stalactite forms, to which I called your 
attention in the earlier part of this paper. These are culti- 
vated for five to six weeks, and, when pure cultures are obtained 
they are killed by raising the temperature to 65° C. for an 
hour, and, as an additional precaution, a small quantity of lysol 
is added. Of this preparation, from 0*5 to 4 c.c. are injected, 
according to the age and size of the individual treated. Sus- 
ceptibility to plague is reduced by about one-fourth, and of 
those attacked after previous inoculation the mortality 
is only about one-fourth of what it is among the non- 
inoculated. 
We have not yet got accurate knowledge as to the length 
of time this inoculation confers protection : it probably is 
for a year, and possibly even longer. 
Preventive Measures 
Now that you have learnt what plague is and how it is 
spread, you will readily see that preventive measures must be 
directed against the rat and the rat-flea. 
The United States Public Health Service have outlined 
such measures in a very succinct form. 
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