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pestis is absent or at least difficult to find. I have never yet been able to make cultures direct from such buboes, even although these were just developing. Notwithstanding the utmost precautions, cocci were always found present, and the presence of these were even found in microscopic preparations of smears of the bubo, stained by GRAM's method. In conclusion, my experience leads me to believe that the puriform discharge from a suppurating bubo, is not dangerous so far as plague infection is concerned.
II. Indirect Elimination.-In order for such a process to take place, two conditions must be fulfilled. In the first, the causal germs must be present in the blood stream, and in the second, these germs must pass the barriers set up by the secreting epithelium. In my opinion, the first of these conditions is fulfilled in the case of plague. It is in reality a septicemic disorder. The B. pestis is found in the general circulation and multiplies there.
The fate awaiting the bacilli in the blood is of a varied nature. The bac- tericidal action of the blood itself accounts for the death of a few bacilli. Others meet their end in the spleen and bone marrow. The pathological condition of the blood is of great interest in plague. There would appear to be little known in regard to its conditions in such a disease. Several interesting points have been observed by myself in regard to plague blood, but I do not venture to furnish details at present owing to the incompleteness of my results.
In regard to the part played by the various secretions and excretions, one may say the following. The kidneys, under physiological circumstances, do not eliminate micro-organisms (WYSSO-KOWITSCH). In plague, the kidneys almost always participate in the general pathological process. Albumin is present in the urine, and there is every reason to believe that plague bacilli are actively elimin- ated in the urine.
Just as in other diseases, the condition of the urine, and other excretions are of great importance in regard to their infectivity in convalescent cases of plague and in latent cases of the disease. In typhoid and many other infectious diseases, the causal agents are known to harbour in the body for considerable periods of time. They rarely reinfect an individual who harbours them, but are of suffi- cient virulence to occasion widespread infection.
In plague, the same method obtains importance. Such bacilli are either con- stantly or periodically discharged from the body and unless destroyed constitute fresh foci of infection.
The question in regard to latent cases in plague is of equally great signifi- cance. That latency in infectious disease is an important factor in influencing the principles of prophylaxis is becoming more and more recognised daily. I see no reason to doubt the occurrence of latent plague in man. The researches of GOTSCHLICH, BITTER and many others are a sufficient guarantee of its frequent occurrence. I am convinced of its presence amongst rats. Many instances of such in rats have come before my notice.
Latent plague in rats would appear to be an important factor in regard to the bridging over of plague epidemics in rats and man.
I have no data of my own in regard to the elimination of the B. pestis through the other secretions of the body, e.g., the salivary, lacrymal, intestinal or sebaceous glands, etc.
WILLIAM HUNTER.
The Significance of Air as a Carrier of Plague Infection.
The significance of air in the spread of infectious diseases has been thoroughly investigated by FLÜGGE and his school. It has been demonstrated that the trans- mission of disease by such a means must be occasioned by one of two methods :-
(1.) By dust.
(2.) By so called drop infection.