24 



SCIENCE 



[N. S. Vol. XXXIV. No. 862 



regard. The schools seem to have met the 

 new arrangements with cordiality and good 

 spirit. — Harvard Alumni Bulletin. 



SCIENTIFIC BOOKS 

 Reports to the Local Government Board on 



Public Health and Medical Suhjects (New 



Series, No. 53). Further Eeports (No. 4) 



on Flies as Carriers of Infection. Pp. 48. 



Bacon Street, E., London, Darling and Son, 



Limited. 1911. 



This latest number of this very valuable 

 series of reports on flies as carriers of infec- 

 tion includes four articles of cosmopolitan 

 interest: Dr. Copeman, Mr. Hewlett and Mr. 

 Merriman report upon an experimental in- 

 vestigation in the range of flight of flies; Mr. 

 Austen presents a memorandum on the result 

 of examinations of flies from Postwick Vil- 

 lage and refuse deposit; Dr. NicoU discusses 

 the part played by flies in the dispersal of the 

 eggs of parasitic worms, and Dr. Graham- 

 Smith gives further observations on the ways 

 in which artificially infected flies carry and 

 distribute pathogenic and other bacteria. 



The investigation on the range of flight of 

 flies, by Dr. Copeman, Mr. Hewlett and Mr. 

 Merriman, is of great importance and is one 

 which is very difficult to carry to a practical 

 conclusion. Its value in deciding, in prac- 

 tical anti-fly work, the distance from a given 

 point to which it is necessary to carry the 

 abolition of possible breeding places is funda- 

 mental. It necessitates the use of a method 

 of marking flies which will not interfere with 

 their normal habits, and can at the best indi- 

 cate only certainties of observation. It is 

 shown in this report that marked flies in the 

 series of observations were recovered at dis- 

 tances varying from 400 yards to 1,408 yards 

 from the point where they were marked, thus 

 indicating a flight of more than three quar- 

 ters of a mile. The writer of this notice, in 

 his recently published book " The House Fly 

 — ^Disease Carrier," brought together all of 

 the previously recorded observations on this 

 point, but was unable to find any substantial 

 records of distances equal to this. While it 

 is true that the probabilities strongly favor a 



more extended flight, these observations never- 

 theless record the longest scientifically ob- 

 served flight and indicate that for at least 

 three quarters of a mile around a given point 

 breeding places must be treated or abolished 

 if the nuisance and danger of the house fly 

 are to be avoided. It should be stated that, 

 in the text on page 8, a distance of 1,700 

 yards is indicated, but this does not appear 

 in the table. Accepting 1,700 yards, the ob- 

 served limit of distribution reaches nearly a 

 mile. The authors note that the direction of 

 the prevailing wind is an important factor, 

 and that the time of the distribution observa- 

 tions was forty-eight hours. 



Dr. Nicoll, in his consideration of the part 

 played by flies in the dispersal of the eggs of 

 parasitic worms, shows that flies may convey 

 such eggs from excrement to food in two 

 ways, namely, on the external surface of the 

 body and in the intestine. The latter mode 

 occurs only where the eggs are of smaU size 

 (under 0.05 mm. in diameter). Larger eggs 

 may be carried on the external surface, but 

 these are usually removed by the fly within a 

 short time. Others which are taken into the 

 intestine may remain there for two days or 

 longer, and may remain alive and subse- 

 quently cause infection. The eggs of the fol- 

 lowing parasitic worms have been shown ex- 

 perimentally to be capable of being carried by 

 Musca domestica: Twnia solium, Tcenia ser- 

 rata, Tcenia marginata, Hymenolepis nana, 

 Dipylidium caninum, Dihothriocephalus la- 

 tus ( V), Oxyuris vermicular is, Trichuris {Tri- 

 chocephalus) trichiurus, both internally and 

 externally; Necator americanus, Ankylostoma 

 caninum, Bclerostomum equinum, Ascaris 

 megalocephala, Toxascaris limhata (^Ascaris 

 canis e. p.), Hymenolepis diminuta externally 

 only. No Trematode parasites have as yet 

 been experimented with in this investigation. 



Dr. Graham-Smith concludes that both 

 house flies and blow-flies are capable of infect- 

 ing fluids, such as milk and syrup, on which 

 they feed and into which they fall. In the 

 case of the house fly, infected with certain 

 micro-organisms {B. prodigiosus and B. an- 

 thracis), gross infection may be produced in 



