340 



SCIENCE. 



[N. S. Vol. XXII. No. 559. 



our side the Atlantic, since the passing of the 

 fathers of the last generation, have quite reck- 

 lessly transgressed, and I, as one of the chief 

 among the transgressors, acknowledge the 

 justice of the reprimand. 



It will be questioned that the Vienna con- 

 gress was truly and fairly international. 

 Many will deny that its regulations are of 

 binding force; and let all that even be denied. 

 Yet the laws that are unwritten are some- 

 times, it may be, the most binding of all; 

 and I can but regard this expression of the 

 congress as its most important pronounce- 

 ment; and viewed — if one so view it — as a 

 mere recommendation, it is a most wholesome 

 one. Edw. L. Greene. 



National Museum, 

 Washi]?^gton, D. C. 



fleas and disease. 

 A NEW and very striking interest now at- 

 taches to investigations relative to the connec- 

 tion of fleas with the transmission of disease, 

 in view of the recent specific statements that 

 have been made in connection with the trans- 

 mission of leprosy by these insects. It is per-- 

 fectly true that we have very little definite 

 knowledge of the whole matter and that opin- 

 ions so far expressed are almost purely theo- 

 retical. An excellent historical resume of the 

 subject is given by Dr. Herzog in Bulletin No. 

 23 of the Bureau of Government Laboratories 

 at Manila. He tells of various efforts to find 

 plague bacilli in fleas or to produce the dis- 

 ease by allowing fleas from diseased rats to 

 bite healthy individuals. Here he might 

 have referred back to Yersin's experience in 

 failing to find the bacilli in the blood from 

 other parts of the body when they were raulti- 

 tudinous in the buboes, and he should have 

 suggested that a flea might have a similar ex- 

 perience. Such a view-point might invalidate 

 much if not most of the experimental work so 

 far accomplished. The ' severe and just ' 

 criticisms of Galli-Yalerio, made at a time 

 when he was not even acquainted with the 

 species of fleas infesting rats in regions 

 ravaged by the plague, are scarcely worthy of 

 consideration one way or the other. The only 

 serious work on the subject was begun at Syd- 



ney, where there w^as a proper effort to first 

 know the fleas and then to determine if any of 

 the species infesting rats would also bite human 

 beings. Investigators there found Pulex palli- 

 dus common on rats. This is a very near rela- 

 tive of P. irritans and was experimentally de- 

 termined as able and willing to bite human 

 beings, as might have been expected theoretic- 

 ally. The singling out of this species frora 

 all the others found there on rats was a dis- 

 tinct step in advance. 



The verdict of the Indian Plague Com- 

 mission was : No evidence, one way or the 

 other. Indeed, all the way through this dis- 

 cussion, a point that strikes the unprejudiced 

 reader more strongly than any other is the 

 startling paucity of facts — actual observations 

 and experiments — on which all the theories, 

 for and against, have been built. Apparently 

 the most categorical statements are coming 

 from men who do not know the rat fleas of the 

 tropics and subtropics at all. Dr. Herzog 

 adds nothing in the way of adequate experi- 

 ment, but submits the description of a ' new 

 rat flea ' — Pulex philippinensis — which may or 

 may not be new, since the description does not 

 include a single diagnostic character to make 

 possible comparisons with any other species. 

 The photographs presented, which are exceed- 

 ingly poor in detail, indicate a form extremely 

 close to Pulex irritans, the flea sjpecific to 

 human beings, which species has, by the way, 

 been taken from rats, cats, dogs, foxes and 

 other animals in regions where it is abundant, 

 a fact of striking importance in this investi- 

 gation. 



There are some raost important aspects of 

 the case which have as yet not been considered 

 at all. Most fleas are epicures in their blood- 

 sucking habits where mosquitoes are gluttons. 

 They do not settle and gorge themselves, as do 

 the mosquitoes, but pass rapidly from place to 

 place and bite often. A single flea has been 

 observed to bite so as to leave a dozen or more 

 inflamed spots in as many minutes and yet its 

 abdomen show no extraordinary dilation. The 

 flea possesses a remarkable puncturing appa- 

 ratus, portions having the appearance of a 

 double-edged saw, with an intricately de- 

 veloped serration. It seems likely that the 



