5^4 



NATURE 



[July 7, 192 1 



Letters to the Editor. 



\T:he Editoy does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 ' can he Undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous comtnunications.] 



Pathogenic Organisms in the Pollen of Flowers and 

 Disease in Bees. 



The observations of Dr. Rennie and his co-workers 

 have established an , association between Acarine in- 

 fection and Isle of Wight disease in bees. There still 

 remains, however, the question of the part played by 

 bacillary infection in this and other diseases which 

 affect bees. In this communication I desire to direct 

 attention to two aspects only of this complex problem. 



(i) In the course of an inquiry during the last three 

 years into an epidemic having many of the features 

 of the so-called Isle of Wight disease, which has 

 caused the loss of a number of my own hives and 

 other stocks in the Midland area, an aerobic short 

 sppre-bearing and gram-negative bacillus resembling 

 B. pestif. apis, as described by Dr. Maldert in 

 the Journal of Agriculture, vol. xv.. No. ii, 

 February, 1909, was obtained in large numbers from 

 the faeces of affected bees from all the diseased stocks, 

 and was readily grown, sometimes in pure culture, in 

 broth, or on agar or serum agar. 



In 1919 I also found that the same organism could 

 be cultured from the sealed cells of the honey- 

 combs from infected hives. A number of cells were 

 opened by removing the cap with a sterilised instru- 

 ment, and platinum loops of honey taken from these 

 sealed cells were added to broth or smeared on an 

 agar or serum agar slope and incubated at 37° C. for 

 36 hours. Numerous colonies of the spore-bearing, 

 gram-negative bacillus were obtained from many of 

 the cells. The organism seems to exist in the honey in 

 the spore form only, no bacillary forms being detected 

 before culture, and no cloudiness or discoloration of 

 the honey being produced. In two cases it grew 

 readily when Obtained from infected honey cells which 

 had remained sealed for more than twelve months. 



The colonies grown from honey resemble those ob- 

 tained by culture from the faeces of affected bees. 

 They are smooth and white when small, but soon 

 show a corrugated brain-like surface, and may be- 

 come slightly yellow or pinkish at a later stage. 



The fact that, as Dr. Maiden showed, the same 

 organism can be obtained from the intestinal contents 

 of apparently healthy bees is important, and I have 

 also grown it from sealed honey cells from apparently 

 healthy hives. Under these conditions the colonies are 

 generally much fewer in number. 



This fact is of interest as bearing on the question 

 of bacillary infection in bees, and also on the problem 

 of the inhibitory effect of honey as a culture medium 

 on the growth of organisms, and. their persistence in 

 the spore form. 



The same organism has also been cultured on the 

 same media from the compressed pollen removed 

 from the thighs of the honey-bee and from several 

 species of humble bee, and also in one case from 

 honey taken from the nest of Bombus lapidarius. 



(2) The second point has reference to the life-history 

 of the organism outside the body of the bee and the 

 honey dell. 



In 19 19 I commenced to investigate pollen from 

 various kinds of flowers frequented and avoided by 



NO. 2697, VOL. 107] 



bees, and in the case of frequented flowers both 

 before and after the opening of the flower. 



It is ihipossible here to describe in detail the large 

 number of experiments carried out on different kinds 

 of flowers. Speaking generally, the spore-bearing, 

 gram-negative bacillus described above, together with 

 other bacillary, and in some cases coccal, forms, were 

 frequently grown from the pollen of flowers frequented 

 by the honey-bee, various species of wild bee, and 

 some other insects, while colonies were absent or were 

 sparsely grown from unopened flowers and from 

 flowers such as the edible and sweet pea and others 

 which are not visited by bees to the same extent. 

 Pollen from the pine and other wind-fertilised trees 

 gave very few colonies. From the pollen at the 

 bottom of the spathe of an arum (Arum maculatum), 

 in which numerous flies were imprisoned, a small 

 coccus grew freely, in addition to the bacillus form. 



There can be no doubt that the anthers and pistils 

 of flowers visited by bees and other insects provide 

 the chief sites of implantation and dispersal grounds 

 for organisms which pass a portion of their life- 

 history in the alimentary canal of bees and in stored 

 honey. 



Further investigation is necessary to decide what 

 effect, if any, exposure to atmospheric conditions and 

 to pollen and to plant secretions exercise on the 

 growth of these organisms. 



It seems probable that many kinds of flowers, 

 esf>ecially open flowers, frequented by bees and other 

 insects harbour enormous numbers of organisms, 

 some of which at any rate are pathogenic to bees 

 under certain conditions, and that a t^urther study 

 of the bacterial flora of flowers would shed light on 

 the diseases of bees and other insects, and possibly on 

 some diseases which affect animals and even man. 



C. J. Bond. 



the Nature of the Electrical Conductivity of Glass. 



In the course of some work on the electrical con- 

 ductivity of some dielectrics, which was recently 

 described before the Royal Dublin Society and forms 

 the subject of a forthcoming paper in the Philo- 

 sophical Magazine, the question arose as to the 

 possible electrolytic nature of the current in the case 

 of materials such as glass. The following simple 

 experiment, which is, I think, new, seems worthy of 

 record as affording evidence against this view. 



A thin glass bulb about i-8 cm. in diameter was 

 blown at the end of a piece of tubing, the whole 

 being then filled with a dilute neutral solution of 

 calcium chloride containing a little phenolphthalein. 

 The bulb was immersed in a small beaker of tap- 

 water placed on an insulating stand. Electrodes were 

 placed in the upper part of the tube and in the beaker, 

 one being connected to a source maintained at about 

 — 8000 volts with the aid of rectifying valves, and the 

 other to earth through a sensitive galvanometer. 

 Thus a known current could be passed through the 

 glass wall of the bulb in either direction. Currents 

 leaking along the exterior surface of the glass tube 

 were prevented from passing through the galvano- 

 meter by an earthed strip of tinfoil gummed round 

 the tube as a guard ring. 



The bulb and tube were filled the day before the 

 test was made, and in the interval a slight pink 

 colour had developed, indicating the solution of a 

 little alkali from the glass. The central electrode was 

 first used as anode, so that the glass of the bulb 

 acted as cathode to the solution. If the bulb con- 

 ducts like a metal, we should expect a red colour to 

 develop on its surface owing to electrolysis of the 

 solution. If, however, the current through the glass 



