(1) The question of the alleged spread of infection by direct contact with a suffering case has been discussed. Our observations in a plague hospital and with material obtained from this hospital lead us to conclude that such a mode of spread does not exist. Support is given to this view by a consideration of the influence of imported cases on the spread of the epidemic and by an investigation of the relative frequency of single and multiple cases in houses and buildings. We have, further, referred to our experience that a rat epizootic is alone sufficient to account for a widespread dissemination of infection throughout a locality. A review of the whole of the evidence on this point brings us to the conclusion that contact with plague cases plays no part in the spread of the epidemic.
(2) In discussing the question of the infectivity of houses, evidence has been brought forward which points to the rat flea being the transmitting agent of infection from rat to man. Further, reasons have been given for the view that plague does not persist in a locality apart from infection amongst the rats.
(3) From arguments brought forward in the discussion of the two previous questions we conclude that the epidemic is wholly dependent upon the epizootics.
(4) It has been shown that infection may be transported to a distance by means of rat fleas in clothing or merchandise and that such infection, when imported into a hitherto uninfected locality, may give rise to an epizootic in the rats.
(5) Our observations lead us to conclude that plague in domestic animals in Bombay either does not occur or occurs so seldom that it cannot be said to possess any significance from an epidemiological standpoint.