September 15, 1905.1 



SCIENCE. 



341 



flea would have difficulty in wiping its inouth 

 clean after a meal, and indeed microscopical 

 examination made soon after a flea has bitten 

 will reveal blood upon its external mouth 

 parts. If these are snipped ofi: and teased out 

 in a drop of water many blood corpuscles may 

 be found, and if these occur then surely it 

 would be possible for numberless bacilli to 

 lodge there also. This is merely a suggestion 

 — no one known to me has examined the mat- 

 ter properly. Theoretically, a flea drinking 

 blood from a malignant buboe would be pretty 

 likely to have a stomach well filled with the 

 bacilli, and this is said to be the case with the 

 plague as well as with leprosy, though what 

 future relation material that has once passed 

 the flea's throat may have to human beings it 

 is for the bacteriologist to discover, if, indeed, 

 this fact has any bearing of importance what- 

 ever. According to Dr. Herzog, Zirolia says 

 that ' the feces of fleas from plague-infected 

 animals contain virulent bacilli, and that in 

 the bodies of the dead fleas these parasites sur- 

 vive for a long time,' though as usual, one of 

 the most important facts — the name of the flea 

 studied — is not given. If a flea bites a ma- 

 lignant buboe and then passes to a healthy in- 

 dividual and inserts the proboscis above des- 

 cribed beneath the skin, the bacteriologist is 

 to say what chance there is for inoculation 

 in the inflamed flea-bite, certainly a better 

 chance than with a thrust made by a needle. 

 Seemingly there is alraost a physical impossi- 

 bility that bacilli should not be transferred. 

 In the case of leprosy, a flea which has inserted 

 the above-described proboscis into a malignant 

 lepra blotch is persona non grata so far as I 

 am concerned — I would rather not have him 

 transfer his attention to any part of my body, 

 even though I be in more or less ignorance of 

 , the possibilities of the case as related to actual 

 infection, resistance or receptivity of diiferent 

 tissues inoculated, etc. Such a statement as 

 Dr. Herzog makes concerning the work of 

 Thompson at Sydney must, it seems to me, 

 serve as a striking call for further investiga- 

 tion. He says, ' Thompson observed blebs 

 which he considered to be produced by fleas 

 and to be the place of entrance of the plague 

 virus, concluding that the transmission of 



plague from rats and mice through the inter- 

 mediation of fleas must be freqtient.' 



The conflict of opinion all along the line 

 has been amusing when the almost utter lack 

 of definite knowledge on the subject is con- 

 sidered. For . instance, in all the talk of rat 

 fleas biting human beings, scarcely a mention 

 has been made of Pulex irritans biting rats, 

 though where this species is abundant this is a 

 common occurrence. All theories must be ex- 

 amined, however improbable, from every point 

 of view, and thoroughly sifted, and then the 

 workable residue may form a useful guide for 

 the broadly planned and properly executed ex- 

 perimentation of the future — the only kind of 

 work that will really count. 



Surely here is a subject of prime importance 

 calling loudly for systematic and thorough 

 investigation. For after the years of work of 

 specialists and commissions, the plague is still 

 claiming its thousands, and is now on our own 

 shores, and we have to make the fearful ad- 

 mission that the dread blight of leprosy has 

 not only a firm foothold within the United 

 States, but is rapidly spreading, as new locali- 

 ties become infected. It seems as if even the 

 few considerations mentioned above indicated 

 clearly and definitely abundant need for the 

 following initiative lines of work: 



I. Extensive collecting of the fleas infesting 

 rats, cats, dogs and especially human heings, 

 in all parts of the world, iut more particularly 

 and thoroughly in all plague- and leprosy- 

 infested regions. Of such prime importance 

 does the writer consider this preliminary inves- 

 tigation that he recently offered to take all the 

 risks incident to such work and prosecute it 

 vigorously and thoroughly in all the worst 

 plague- and leprosy-infested regions. His 

 somewhat extended experience in tropical 

 field work and special knowledge of the subject 

 seemed to justify and call for such an offer. 

 Whether it will elicit any response remains to 

 be seen. The striking need of the investiga- 

 tion can not be doubted. 



II. An extended and thorough systematic 

 and anatomic study of the species as is now 

 heing carried on hy the United States govern- 

 ment in the case of mosquitoes. The writer 

 has had such work in progress at his personal 



