26 



KNOWLEDGE. 



January. 1911. 



Analyses of the body of Mycenian vases showed that they 

 contained from approximately 41 to 48 per cent, of silica, 

 17 to 20 per cent, of alumina, 7 to 9 per cent, of iron oxide. 

 14 to 20 per cent, of lime. 4'5 per cent, of magnesia, about 

 3 per cent, of potassium oxide and about 5'5 per cent, of 

 carbonate. From these analyses it appears that Mycenian 

 pottery differs from Attic and Campanian pottery in containing 

 much less silica but much more lime, and in the relatively 

 large proportion of carbonate present. Owing to its low 

 proportion in silica the pottery can be readily melted at a 

 relatively low temperature. 



THE DIGESTIBILirV OF BLEACHED FLOL'R.— 

 Of the numerous methods that have been proposed for bleach- 

 ing flour, only those in which nitrogen 

 peroxide is employed as the bleaching agent 

 have proved successful upon a commercial 

 scale. Flour bleached in this manner is now 

 largely sold, and on more than one occasion 

 has been the subject of actions in the law 

 courts. Hence the experiments of Mr. E. \V. 

 RocUwood upon the effect of bleaching 

 upon the digestibility of flour ijouni. Biol. 

 CJicni.. 1910, viii, 3271 have a special 

 intei-cst at the present time. In these 

 experiments the tests were applied simul- 

 taneously to bleached and unbleached 

 samples of the same flour, the conditions in 

 each case being strictly parallel. It was found 

 that uncooked gluten separated from the flours 

 was digested by pepsin with equal rapidity in 

 each instance, while the product from the 

 bleached flour was digested more readily by 

 pancreatin than that from tlie unbleached 

 specimen. The cooked gluten from the 

 bleached flour was more easily digested 

 both by pepsin and pancreatin than that 

 from unbleached flour, while bread made 

 from the two kinds of flour did not differ in 

 its digestibility, the nitrous compound having 

 been expelled during the baking. The bleach- 

 ing process was also found to have had no 

 appreciable influence upon the digestibility of the starch in 

 the flour. 



THE MEKliK BURNER. — A new gas burner, presenting 

 many advantages over the ordinary Bunsen burner, has been 

 put upon the market by the Cambridge Scientific Instrument 

 Company, under the name of the Meker burner. The con- 

 struction of this is sliown in the accompanying figure, from 

 which it will be seen that the holes for the admission of air 

 are much larger than in the Bunsen burner, so that the 

 mixture of air and gas in the chimney is of the right proportion 

 for complete combustion. A deep grid of nickel is screwed to 

 the top of the burner to prevent the flame " striking back." 

 The flame of this burner is homogeneous, and does not show 

 the inner and outer cone of the Bunsen flame. Its temperature 

 is much higher than that of the latter, and is nearly uniform 

 throughout. In fact, the coolest part of a Meker flame is 

 hotter than the hottest portion of a Bunsen flame. A burner 

 of modified form has been made for use with compressed air, 

 thus enabling a yet higher temperature to be reached. 



FXONOMIC BIOLOCY. 



By Walthr E. Collinge, M.Sc, F.L.S., F.E.S. 



HOUSE FLIES AND DISEASE. — I promised last 

 month to deal with some of the correspondence I have 

 received with reference to house flies as transmitters of 

 disease. A renewed interest, I am pleased to say, has been 

 awakened in the subject, and, as I recently stated. I trust the 

 public will ultimately educate the authorities in order that our 

 different public bodies will realize the seriousness of the 

 matter. No one wishes to create a scare, or to indulge in 





Pion of nickel qf'd C 



wild unguarded statements, but to calmly and judicially 

 consider the facts as brought out by recent investigations. 



FLIES IN WINTER. — One correspondent inquires what 

 becomes of the flies in winter, — do they die, leaving eggs to 

 hatch later, or do they hibernate? Mr. F. P. Jepson has 

 shown iJoKi-n. Ecoii. Biol., 1909, vol. iv.) by marking flies in 

 the summer of 1908, for purposes of identification, that 

 nearly all of them were captured in a bakehouse, the supply 

 continuing up to nearly the middle of November, when a 

 sudden sharp frost seemingly caused their sudden disap- 

 pearance; they reappeared, however, on February 15th, 1909. 

 From these and other experiments he concludes that during 

 the winter flies may be found where the conditions — tempera- 

 ture and so on — are favourable, and 

 ^ that they will breed in the winter. Many 



undoubtedly persist throughout the winter 

 as adults, and appear to be more hardy 

 and longer lived than those taken in the 

 summer. 



IRE 1. 



er Burner 



I H !•: SPREAD (IF INFECTIVE 

 niSE.\SES. — The belief that flies may 

 carry the germs of difterent diseases dates 

 back to the sixteenth century, but actual 

 experiments proving this are of much more 

 recent date. Experiment has now actually 

 demonstrated that the following diseases 

 can be disseminated by the agency of house- 

 flies : — Anthrax, cliolera. ophthalmia, tuber- 

 culosis and typhoid fever. In addition to 

 these there are a number of diseases which 

 ai"e probably carried by flies, but the 

 evidence, as yet, is incouclusixe. 



There is now evidence sufficiently clear 

 to show that, apart from disseminating the 

 germs of the above diseases, flies also carry 

 the eggs of parasitic worms and various 

 species of fungi. 



Professor Nuttall very pertinently re- 

 marks (Local Government Board Report, 

 No. 10, 19091: — "It should be remembered that a fly 

 may cause relati\el\- gross infection of any food upon 

 which it alights after having fed upon infecti\e substances, 

 be they tvphoid, cholera or diarrhoea stools. Not only 

 IS its exterior contaminated, but its intestine is charged 

 with infective material in concentrated form which may be 

 discharged undigested upon fresh food which it seeks. 

 Consequently, the excrement voided by a single fly may 

 contain a greater quantity of the infective agents than, 

 for instance, a sajuple of infected water. In potential 

 possibilities the droppings of one fly may. in certain circum- 

 stances, weigh in the balance as against buckets of water or 

 of milk." 



PROGRESS OF THE WORK.— Our grand-parents would 

 ha\e laughed at the idea of attempting to control such ubiqui- 

 tous pests as house-flies ; indeed, there are still people who are 

 unconvinced as to the seriousness of the part these insects 

 play in every-day life, as is instanced by many of the letters I 

 have received during the past two months; but, thanks to the 

 excellent work that is being carried out at Cambridge and else- 

 where, it will not be long before the public are not only 

 convinced, but they w^ill make themselves heard for drastic 

 alterations that will tend to minimise the danger. 



Dr. Monckton Copeman has recently scheduled (Local 

 Government Board Report, No. 40, 1910) the work that is 

 being done at Cambridge, which includes special attention to 

 the elucidation of the question as to the range of flight of 

 flies, both in horizontal and vertical directions ; and under 

 varying conditions, meteorological and otherwise. Trials are 

 to be made of the respective value of various baits for 

 attracting and killing flies. The so-called lesser house-fly. 



