122 



PORTAL OF ENTRANCE OF THE VIRUS. 



As is well known, the portal of entrance of the plague virus can 

 not always be found. In the sixteen bubonic cases there were 

 seven in which even the slightest indication of the probable portal 

 of entrance was absent (cases Nos. 1, 5, 6, 7, 8, 12, and 14). In 

 the majority of the remaining nine cases of bubonic plague proper 

 the portal of entrance was more or less unmistakably indicated. But 

 in connection with this subject one must not forget that a secondary 

 skin plague lesion might be mistaken for the primary portal of 

 entrance. This is of course particularly liable to happen in cases 

 in which but little, if anything, is known of the clinical history. 

 Where a reliable clinical history can be obtained such a mistake 

 is less liable to occur. In the three pneumonic cases, the portal 

 of entrance of the virus was the lungs, because the changes in the 

 bronchial glands were such as to destroy the probability of their 

 being the first focus of infection. In case No. 20 — primary plague 

 septicaemia — there was no evidence of an intestinal origin ; however, 

 one might in this case suppose that the bacilli were inhaled, without 

 causing a distinct pneumonia, entering the blood current almost 

 immediately and in this manner producing a general septicaemia 

 without any manifest focal localization. 



PERIOD OF INCUBATION. 



The period of incubation of plague, as a rule, is a short one. The 

 Indian Plague Commission has compiled a table of cases in which 

 the time of infection could be fixed beyond doubt, it being contracted 

 during post-mortem examinations or during some similar manipula- 

 tion of fatal human plague cases. From their table it appears that 

 the period of incubation generally ranges from one to five days. 



"While thus," the report of the Commission (Vol. V, p. 88) says, 

 "no facts have been reported to us which establish that the incubation 

 period may be prolonged beyond the period of five days, the limit fixed 

 by the numerous cases detailed above, * * * we think that it is 

 a matter of importance to point out, that where the plague first takes the 

 form of pestis minor, and where afterwards pestis minor develops, owing 

 to some subsequent loss of resisting power, into typical bubonic plague, 

 there is a possibility of a considerable interval elapsing between the time 

 at which the infection was contracted and the time at which the clinical 

 symptoms became typical. Such cases. Important as they are in the 

 epidemiological study of the disease, as indicating one of the possible 



