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Again in such cases where a definite point of inoculation was found in the skin, a certain amount of lymphangitis was always present. In the case already detailed, it was present to a marked degree. In others, I have found it equally well pronounced. The exact etiology of this lymphangitis has not been determined. Whether it is the direct result of the B. pestis by itself or due to other micro-orga- nisms, e.g., the streptococcus, acting alone or in conjunction with the plague bacillus, I have found difficult to determine.
The fact that this lymphangitis is present in cases in which a definite point of inoculation is present, makes one sceptical as to the occurrence of infection through the skin. Further details in regard to this question will be given under the pathological section of this research.
It may be as well to mention incidentally at this point, that in the post- mortem room, I have constantly found the B. pestis in the heart blood ́and spleen in cases of bubonic plague. It is generally acknowledged that during the period immediately before death, the organisms swarm into the blood stream.
In connection with the actual bubonic swellings themselves, it would appear to be of importance to determine what part the B. pestis actually takes in their formation. We have to consider, whether the B. pestis in pure culture produces the typical pathological lesion, or whether such buboes are the result of the growth of the plague bacillus plus pyogenic bacteria, the latter by their more active growth eventually causing a disappearance of the B. pestis itself.
Another important type of plague is what is known as Plague Pneumonia or lung pest. Its occurrence is subject to much variation. It may form the chief variety met with during an epidemic; at other times it is almost entirely absent. Again it may be the type of plague most frequently found at the commencement of an epidemic, or be more or less incidentally met with throughout the whole duration of the epidemic. Its frequency and appearance is therefore subject to considerable variation. The reasons for this, are by no means obvious. however may be said, that outbreaks of this type of the disease are usually fol lowed by severe and very fatal epidemics, and a good instance of this is found in the well known Black Death, an epidemic in which this type of the disease made felt its utmost severity.
This
The prevalence of pneumonic plague in Hongkong has fortunately not been marked. It has been met with chiefly in young children.
The point requiring discussion at present is the nature of this pneumonic process. What constitutes primary and secondary pneumonia?
That the B. pes- tis is able to set up à condition resembling pneumonia, may be said to be firmly established through the observations of CHILDE and others in Bombay and other parts of India.
In my opinion these pneumonias are either primary or secondary. Primary pneumonic plague is a pathological condition set up in the lungs as a result of direct inhalation of the B. pestis. Secondary pneumonic plague is merely one of the many manifestations of septicamic plague. In fact buboes and pneumonia may be present together in a septicemic case of plague.
It would appear that the pneumonias met with in Hongkong are secondary to blood infection. In the cases which occurred during the epidemic of 1903, the blood was examined during the early stages of the disease and plague bacilli were
found.
So far as primary plague pneumonia is concerned are we to regard this dis- ease as due to the produce of plague bacilli in the lungs alone, or does a certain degree of blood infection occur at the same time? In the light of most modern bacteriological research, we are bound to admit that in such cases, blood infection does occur.
Reviewing the whole question of plague from a clinical and bacteriological standpoint we are reduced to two main types of the disease, namely:-
1. Plague septicœmia.
2. Prmiary plaque pneumonia.
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