February 2, 1893] 



NATURE 



000 



found to be the following, and it has the additional merit of 

 enabling us to prove, beyond all doubt, that the ripe spores of 

 Bacillus anthracii are really inhibited or killed by sunlight. 



A few c.c. of sterile distilled water in a tube are thoroughly 

 saturated with the anthrax spores taken from an old culture which 

 has never been exposed to light, and the tube placed for twenty- 

 four hours at 56° C. ; this kills all immature spores, bacilli, 

 and enzymes, and leaves us with a crop of the most resistant and 

 fully matured virulent spores. 



Experiments with such spores have been made to determine 

 the relative power of the different rays of the spectrum to destroy 

 the anthrax. 



It is necessary to note first, however, that in experimenting 

 with the electric light, although but few exposures have been 

 made as yet, it is evident that its effects are feebler than those of 

 the winter sun. 



At present it has only been possible to observe that the in- 

 hibiting effects are stronger at the blue end of the spectrum than 

 at the red, and exposures to sunlight passing through coloured 

 glasses confirm this result ; but the observations are being con- 

 tinued in the hope of getting a perfectly sharp record of the 

 effects of each set of rays. 



The following series of experiments are quoted in detail, 

 because they teach several details of importance, in addition to 

 proving the main fact. 



On December 7 three gelatine plates and five agar plates were 

 prepared with spores from a very vigorous and virulent agar tube 

 of anthrax. The spores, which were quite mature, were not 

 subjected to heat, but simply shaken in sterile water to wash and 

 separate them thoroughly. 



The three gelatine plates were made at 35° C, the agar plates 

 at 60° C, neither of which temperatures could injure the ripe 

 spores. 



The three gelatine plates were labelled p i, p 2, and / 3, and 

 the agar plates / 4 to / 8 in order. 



Immediately after making the plates, all were exposed to the 

 December sun, except plates / 4, / 5, and/ 6, and this was 

 done as follows : — In each case the plate had a stencil plate 

 with a cut- out letter on its lower face, and arranged as described 

 above. 



/ I, a gelatine plate with a large letter M, was exposed, face 

 down, to the light reflected from a mirror (see Fig. i) for three 

 hours on December 7, and for four hours on December 8, the 

 interval being passed in a cold room (/ about 8°-9" C), and then 

 incubated at 20° in the dark. 



/ 8 was treated in exactly the same manner. But this was an 

 agar plate with a large W. 



/ 2, a gelatine plate with a large H, was exposed and heated 

 in the same way, except that no mirror was used, the latter 

 being upwards towards the sun. 



/ 3» a gelatine plate with a large B, was similarly exposed, 

 face up, but a plane mirror arranged to reflect light down 

 upon it. 



/ 7, an agar plate with a large E, was treated exactly as the 

 last. 



There now remain the three agar plates, /> 4, /> 5, and / 6, to 

 account for. 

 / 4 was placed forthwith in the dark incubator at 20° C. 

 / 5 and / 6 were kept for eighteen hours in a drawer, the 

 average temperature of which is almost 16° C, and were not 

 exposed till next day (December 8), when they lay for five hours, 

 face upwards, and with a mirror above them. / 5 had a small 

 E, and /6a broad but small I to let the light in. 



After exposure, these also were put in the same incubator 

 with the others. 



Nothing was visible to the unaided eye on these plates (ex- 

 cept/4) until the nth instant, though the microscope showed 

 that germination was proceeding on the loth. The plate/ 4, 

 however, had a distinct veil of colonies all over it on the 9th, 

 and this had developed to a dense typical growth by the iiih. 



On December 11, at 10 a.m., the state of affairs, as regards 

 the exposed plates, was as follows : — 



/ 5 and / 6 showed each a sharp transparent letter — E and I re- 

 spectively — of clear agar in a dull grey matrix of strong anthrax 

 colonies, which covered all the unexposed parts of the plate. 

 [ P I, p 2, and / 3 showed in each case a perfectly clear central 



patch, about i^ inches diameter, with anthrax colonies in the 

 j gelatine around. These anthrax colonies were the larger and 

 more vigorous the more distant they -were from the clear centre. 

 In other words, the anthrax spores had begun to germinate, 



NO- I 2 14, VOL. 47] 



and the colonies were growing more vigorously, in centripetal 

 order. 



On / 7 and/ 8 germination was beginning, but the colonies 

 were as yet too young to enable one to judge of the results. 



The first point of interest is to account for the pronounced 

 results in the plates p 5 and/ 6, and the want of sharp outlines 

 in / I, / 2, and / 3, and the explanation seems to be that, 

 owing to the plates 5 and 6 having laid over night at 16° C, 

 the spores began slowly to germinate out, an.l were consequently 

 in their most tender condition when exposed to the sunlight 

 next day. 



The peculiar centripetal order of development of the colonies 

 on plates/ i, / 2, and/ 3 gave rise to the following attempt at 

 explanation. After observing that the clear space in the middle 

 was not due to the centre of the plate being raise 1, and the 

 infected gelatine having run down to the periphery — a possible 

 event with some batches of Petrie's dishes — it was surmised 

 that the large letters employed might give the clue. 



This was found to be the case. The solar rays on entering 

 the plate were largely reflected from the glass lid of the plates, 

 and so produced feebler insolation effects on parts of the plate 

 around the letter ; these effects were naturally feebler and 

 feebler towards the margin, and so the inhibitory action became 

 less pronounced at distances further and further removed from 

 the centre. Those spores, therefore, which were nearest the 

 periphery germinated out first, and those nearer the centre were 

 retarded and more and more in proportion to their proximity to 

 the insolated letter. 



That this is the correct interpretation of the facts follows 

 clearly from the further behaviour of the above plates. 



At 10 p.m. on the llth — i.e. twelve hours after the morning 

 examination — the plates / i, p 2, and / 3 exhibited their re- 

 spective letters M, H, and B quite clearly, in the grey matrix of 

 anthrax which had rapidly developed in the interval, and 

 excepting a slight want of sharpness in the H of/ 2, the results 

 could hardly have been more satisfactory. 



In/ 7 and/ 8 the very faint outlines of the letters were also 

 showing. 



On the I2th, at 8.30 a.m., the gelatine plates had begun to 

 run, and although the M of / I was still intact, and very well 

 marked, / 2 had liquefied completely, so that the H was a clear 

 patch with blurred outlines in the centre. / 3 still showed the 

 outlines of the B, but it was impossible to keep it longer. 



The main point was definitely established, however, and the 

 treatment of the plates proves conclusively that the spores are 

 not killed by high or low temperatures, but by the direct solar 

 rays. 



These experiments are being continued in order to answer 

 some other questions in this connection. 



The gelatine and agar after such exposures as have been 

 described are still capable of supporting a growth of B. anthnuis 

 if fresh spores are sown on them, whence the effects described 

 are not merely due to the sub-strata being spoilt as food material. 



Royal Meteorological Society, January 18. — Dr. C. 

 Theodore Williams, President, in the chair. — After the report 

 had been read, and the officers and council for the ensuing year 

 had been elected, the President delivered an address on the 

 high altitudes of Colorado and their climates, which was illus- 

 trated by a number of lantern slides. — Dr. Williams first noticed 

 the geography of the plateaux of these regions, culminating step 

 by step in the heights of the rocky mountains, and described the 

 lofty peaks, the great parks, the rugged and grand canons, and 

 the rolling prairie, dividing them into four classes of elevations 

 between 5000 and 14,500 feet above sea level. He then dwelt 

 on the meteorology of each of these divisions ; giving the rain- 

 fall and relative humidity, and accounting for its very small per- 

 centage by the moisture being condensed on the mountain ranges 

 of the Sierras lying to the wot of the Rockies ; also noticing the 

 amount of sunshine and of cloudless weather, the maxima and 

 minima temperatures, the wind force.and the barometric pressure. 

 Dr. Williams quoted some striking examples of electrical pheno- 

 mena witnessed on Pike's Peak (14, 147 feet) by the observer of the 

 U.S. Weather Bureau, when during a violent thunderstorm 

 flashes of fire and loud reports, with heavy showers of sleet,sur- 

 rounded the summit in all directions, and brilliant jets of flame 

 of a rose-white colour jumped from point to point on the electric 

 wire, while the cups of the anemometer, which were revolving 

 rapidly, appeared as one solid ring of fire, from which issued a 

 loud rushing and hissing sound. During another storm the 



