JULV 2 1, I9IOJ 



NATURE 



It is necessary to know more concern-ing the precise con- 

 ditions under which the images referred to above were 

 obtained before one can discuss them with safety ; but 

 they are interesting as apparently indicating that the axis 

 of the trunk discharge imiy be free from metallic particles. 



In this connection, however, it must be added that when 

 one directly observes a negative discharge over a photo- 

 graphic plate from an electrode of zinc or magnesium, every 

 line in the fan-like discharge is seen to have the bluish 

 tint characteristic of the metal. Whatever, then, may be 

 the reason for the absence of these fan-like figures from 

 Mr. Lermantoff's images, it must certainly not be 

 attributed to the absence of metallic particles from them. 

 Alfred W. Porter. 



An Interesting Occultation. 



May I direct attention to an interesting phenomenon 

 which will take place on the morning of July 27, viz. the 

 occultation of the star 7) Geminorum by the planet Venus, 

 the particulars of which are ^s follows :— 



Apparent place of r; Geminorum (mag. 3'2-4'2), July 26, 

 R.A. 6h. qm. 26"6s. ; dec. 22° 32' 6'24" N. Apparent place 

 of Venus (geocentric), July 26, i4h. S7'7m. G.M.T., R.A. 

 6h. 9m. 26'6s., dec. 22° 32' 7'2' \. DecUnation at Green- 

 wich, corrected for paralla.x, 22° 32' 2'3". Semidiameter 

 6" 14'. At Greenwich the occultation commences at 

 i4h. 55m., and ends at i4h. 58m. The planet rises at 

 I3h. 43m., and the sun at i6h. 17m. 



On the afternoon of July 28, \'enus is in very close con- 

 junction with y. Geminorum, the positions of the two 

 bodies at 4h. 27m. being as follows : — 



$. R..-\. 6h. 17m. 3o"9s., dec. 22" 33' 58" N., declination 

 (corrected for parallax) 22° 33' 53". }i Geminorum, R..'\. 

 6h. 17m. 30'qs., dec. 22° 33' 43". As the semidiameter of 

 the planet is b'l", the star will be within about 4" from the 

 southern limb. This, of course, occurs during daylight, 

 tut the planet will be above the horizon at the time. It 

 sets about 6h. 8m. 



Dr. Crommelin has kindly looked through these figures 

 and verified them. Arthur BtRNEx. 



52 Prospect Terrace, Hunslet. 



Pwdre Ser. 



The curious belief that shooting stars, when fallen to 

 earth, become lumps of jelly may possibly be explained in 

 the following nianner : — 



The jelly is very probably the plasmodium of a 

 Myxomyccte, such as Spumaria or Physarum. The 

 Plasmodia occur most frequently in damp weather, but are 

 found in lesser numbers throughout the year. Shooting- 

 stars are also seen at all times in the year,, but most 

 plentifully in the autumn. In these islands, the greatest 

 rainfall is also in the autumn months. 



Consequently, by a purely fortuitous coincidence, meteors 

 and Plasmodia are most plentiful in the latter part of the 

 year, the former because the main meteor swarms, in their 

 annual revolution, cross the earth's track at that time, and 

 the latter on account of the greater rainfall. Two striking 

 phenomena are forced on the rustic attention at the same 

 time, the brilliant display in the sky and the mysterious 

 jelly on the grass. Very naturally the two are considered 

 as causally connected, and so the belief may have arisen. 

 An analogous case is that of "cuckoo-spit," the frothy 

 exudation of the larval frog-hopper, Philaenus spumari::s, 

 which appears at the time of the arrival of the cuckoo and 

 disappears about the period of the bird's departure. 

 W. B. Grove. 

 B. MiLWRD Griffiths. 



L niversity Botanical I-aboratory, Birmingham. 



In connection \vith the article on " Pwdre Ser " in 

 Nature of June 23, it is interesting to find, in Admiral 

 Smyth's " Sailor's Word-Book " — one of the richest re- 

 positories of quaint facts and fancies — the term " fallen- 

 star" defined as "A name for the jelly-fish or medusa, 

 frequently thrown ashore iii summer and autumn." 



C. FiTZHUGH TaLMAN. 



U.S. Department of Asrriculture, Central Office of 

 the Weather Bureau, Washington, D.C., July 11. 

 XO. 2125, VOL. 84] 



HOUSE-FLIES AND DISEASE. 

 A LTHOUGH the verification of the belief that the 

 •^~*- cominonest, most widely distributed and truly 

 domestic of insects, Miisca domestica, Linn., was 

 capable of carrying the germs of certain infectious 

 diseases has been one of the noteworthy accomplish- 

 ments af medical science in the last decade, it is a 

 mistake to attach all the credit to those who, within 

 the last few years, have removed the idea from the 

 realms of hypotheses into the world of facts. 



As early as the seventeenth century, Sydenham 

 associated unhealthy conditions with files. Lord Ave- 

 bury, in 1871, regarded flies as "winged sponges 

 spreading hither and thither to carry out the fou! 

 behests of contagion." In addition to other early 

 suggestions, Nicholas, in 1S73, indicated the possible 

 connection of flies with the dissemination of cholera 

 from a case observed by him in 1850 ; Raimbert in 

 1S69 experimentally proved that the house-fly and 

 blowfly were able to transmit the anthrax bacillus ; 

 Davaine in 1S70, and Bollinger in 1874, also showed 

 that the blowfly could carry the anthrax bacillus, an 

 important practical observation. Laveran in 1880 

 demonstrated the ability of flies to carry the infec- 

 tious discharge of conjunctivitis in Egvpt on their 

 proboscides and legs. All these observers assisted in 



Fig. I. — lihtsca domestical Linn. 



the gradual growth of the belief ; but it was in the 

 'eighties of last century, however, that several in- 

 vestigators adduced more convincing bacteriological 

 proof as to the ability of flies to carry pathogenic and 

 other bacteria. In 1S86, Tizzoni and Cattani obtained 

 the cholera spirillum from flies caught in cholera 

 wards. In the same year, Hoffmann found tubercle 

 bacilli in the excreta of flies caught in a room which 

 had previously contained a phthisical patient. Two 

 years later, Celli showed that the tvphoid bacillus was 

 able to pass in a virulent condition through the diges- 

 tive tract of the flv. 



Since the above observations, which are selected 

 from many others, were made, it has been repeatedly 

 shown and proved that house-flies are able to carry 

 these and other bacterial and fungal organisms. 

 What has not been demonstrated is the extent to 

 which flies are not able to carry such micro-organisms. 

 U'hen the habits of flies are considered, it is not a 

 little remarkable that no serious attention was paid 

 to the possibility of flies having any considerable 

 relationship to the dissemination of disease until 

 within the last twelve years. The excessive mortality 

 from typhoid which occurred in the Spanish-.^merican 

 war was the means of directing the attention of 

 such observers as Vaughan and Veeder to the pos- 

 sible relationship of flies to this disease, especially as 



