January— February 1888.] 



PSYCHE. 



11 



interesting suggestion of the use of 

 yeast as an insecticide, made by Dr. 

 Hagen in 1S79, — a suggestion based 

 on the doctrine of Bail (1S61) that 

 Empiisa., Mucor^ and Saccharomyces^ 

 (the fly fungus, the common moulds, 

 and the yeast plant), were merely dif- 

 ferent forms of the same species and 

 mutually interchangeable. The prac- 

 tical test of this theory, as made by 

 Riley, Prentiss, Smith, Cook, Willet, 

 and others, failed to justify the method 

 (although the results seem not to have 

 been critically studied with the micro- 

 scope), and its theoretical foundation 

 has completely vanished, — so high an 

 authority as De Bary referring to it in 

 1884 as an "item in the history of 

 error" (Morph. und biol. der pilze, p. 

 172). 



And finally we come to schizomy- 

 cosis, the most interesting, probably 

 the most important, far the most intri- 

 cate and difiicult, and consequently the 

 least understood of the forms of insect 

 disease, — perhaps, also, the one which, 

 when fully investigated, will throw 

 most light on problems of human pa- 

 thology. It has only been possible 

 within a very few years to study the 

 bacterial diseases of insects satisfac- 

 torily, since the research has had to 

 wait for the development of methods of 

 bacterial research in general, — a devel- 

 opment which did not really reach a 

 stage of advancement sufficient to yield 

 results that could stand the tests of 

 time and repeated experiment until we 

 had the homogeneous immersion ob- 

 jective and the methods of bacterial 

 culture in solid media. A few conclu- 

 sions have, however, now been made 

 clear, — chiefly, so far as this particular 



division of our subject is concerned, by 

 Pasteur and his followers in France. 



It was in 1S67 that Jlacherie or 

 morts Jiai of the silkworm was first 

 discriminated by Pasteur as a distinct 

 contagious bacterial disease, capable 

 of transmission to healthy larvae by in- 

 fection of their food either with fresh 

 excrement, or with the dust of infected 

 silkworm nurseries of the year before. 

 His personal researches were summed 

 up in his classical work in two vol- 

 umes (1S70) Etudes sur les maladies 

 des vers ct soi'e, and these were followed 

 by numerous otlier papers — those of 

 Dr. de Ferry de la Bellone in Actcs et 

 metnoires du Congrhs sericicole ititer- 

 national for 1875 and Comptesrendtis 

 stenographiques of the same congress 

 for 1878, being the ablest and most 

 convincing that have come under my 

 observation. No student of this affec- 

 tion, whose work I have seen, has. 

 made a critical botanical study of the 

 species of bacteria involved, but these 

 have been referred to only in general 

 terms which serve to indicate that they 

 include both bacilli and micrococci. 



Another more recent and unusually 

 successful research is reported by Ches- 

 hire and Cheyne in the yournal of the 

 Royal 7}iicroscopical society of Lon- 

 don (v. 5, p. 585), on the disease of 

 bee larvae known as foul brood, — dem- 

 onstrated by them to be due to an in- 

 testinal Bacillus. 



In America more has been done on 

 these schizoraycoses than on any other 

 insect diseases, — chiefly, so far as sys- 

 tematic investigation goes, at the Illinois 

 state laboratory of natural history. 

 Here we have carefully studied jaun- 

 dice of the silkworm and flacherie of 



