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cannot be regarded as dangerous. GALLI VALERIO (Cent. f. Bakt. Bl. 27), NUT- TALL (Hyd. Rundschau Bd. 9, 1899), KoLLE (Deut. Med. Wochenschr, 1902) and others have shown that SIMOND's conclusions go too far and Preiffer holds the experiments conducted by SIMONDS do not justify so conclusive an opin ion and notes the fact that in In lia insects in general were found to be of no great epidemiological importance.
Without going deeper into detail, it may be said that the general results obtained by direct observation and experiment go to show that as play an unimportant role in the direct spread of plaque. Experiments in regard to this question have also been carried out in Hongkong. In 1902. Professor SIMPSON and myself endeavoured to procure the infection of healthy rats and monkeys by plague infected rat fleas. The results were entirely negativa. The details of these experiments are given in Professer SIMPSON's Plague Report, page 56.
Again in connection with my duties in supervising the routine examination of rats, plague or otherwise, I have frequently hil occasion to examine the nature of the vermin found on these ani nals, I have had these fleas on my hands and arms, giving them an opportunity to bite, but so far they have refused my blood.
I ain strongly of the opinion that fleas are restricte 1, as GAERTNER, KOLLE, GALLI- VALERIO, NUTTALL and others assert, to definite animal species and this coupled with the negative results obtained by experiment, is good established evidence, that plaque infected fleas are of no practical importance in regard to the spread of plague.
ASHBURTON THOMPSON, in his Plague Report for 1902, reports as follows on rat fleas:-"It is found to be well founded that the species of fleas which infest rats seem, on the one hand, not to infest man, but, on the other, to have no repugnance to him."
In general, the production of plague infection in animals by the bite of plague infected fleas is a rarity. Fleas may leave the plague infected body, human or otherwise, and bite healthy subjects, but the question is, do they infect the latter? The general experience in other countries points to a negative reply. Even although the flea contains plague bacilli in its stomach or intestines, there is so far no satisfactory evidence of any danger through the puncture bite of such an insect.
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Bugs. The ordinary bed bug-Cimex lectularis has been held responsible for the spread of plague, but the evidence upon which the conclusion is based is not, on careful analysis, of a convincing nature. Such insects may bite and suck the blood of a plague infected individual. It does not necessarily follow that such bugs are able to communicate the disease directly to other animals or man. The experimental evidence in the case of these insects is almost entirely negative. The most important experimental results were obtained by NUTTALL (John Hopkins Hospital Reports. viii, 1899). Twenty-two bugs were allowed to suck the blood of a mouse dying of plague. The bugs were immediately placed on four healthy mice. None of these nice contracted plague.
Again experiments were made along the same lines with anthrax, chicken cholera, and mouse septicemia, but although mice are extremely susceptible to these diseases, none contracted the diseases after being bitten severely with the infected bugs. I had several opportunites of examining numbers of bugs bacterio- logically for the presence of plague bacilli. These insects were usually obtained from houses in which cases of human plague had occurred. In many instances plague bacilli were found alter emulsions of the animals had been made and cultures and experimental tests applied. Further details are unnecessary as the same remarks apply to buys as already detailed under the subject of fleas.
Pediculi. A number of these insects was obtained from plague patients in the Kennedy Town Hospital. A considerable number was examined but a nega- tive result was obtained. These animals would not appear to play a great part in the spread of plague.
(b) Non-suctorial Insects.-A considerable number of details in regard to this class of insect has already been given. The occurrence of pathogenic bacteria on the body surfaces of flies, cockroaches, etc., has been referred to on several occasions. Plague bacilli were found by myself on the surface of flies and the result confirmed by animal experiment. The observations in regard to the spread
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