244 



NATURE 



\July i 3) 1882 



existing collection of North American antiquities, I can safely 

 assert that they are totally abnormal in character, that is, unlike 

 any pre-Columbian stone carvings thus far found in the United 

 States. They neither show the characteristics of the stone 

 sculptures discovered in mounds, nor do they resemble the well- 

 known specimens of modern Indian art. In short, they are not 

 typical at all, unless, indeed, we deem them sufficiently important 

 to form a type for themselves. Such an importance, however, 

 I cannot concede to them, believing that they originated in com- 

 paratively modern, certainly in post- Columbian, times, and were 

 made by a few individuals of the Indian, or, perhaps, even of 

 the Caucasian, race. The rude attempts at imitatiug animals of 

 the Old World are conclusive evidences that the makers either 

 had seen such animals, or knew at least that they existed. 



The carvings, it should further be taken into account, are 

 executed in soft potstone, a material easily yielding to the effects 

 of exposure, and hence a short lapse of time would have sufficed 

 to give them the appearance of real antiquities. In fine, I con- 

 sider these carvings as a modern intrusion, and would deem it an 

 extremely hazardous attempt to make them the basis for specu- 

 lations bearing on the ethnology of North America. 

 Charles Rau, 

 Curator Department of Antiquities, 

 U.S. National Museum 



Smithsonian Institution, Washington, D.C., June 27 



The Influence of Light on the Development of Bacteria 



In Nature for July 12, 1877, there appeared a short com- 

 munication from Messrs. Downes and Blunt summarising the 

 conclusions at which they had arrived as the result of investiga- 

 tions on the influence of light on the development of lower 

 organisms. The experiments were described in detail in the 

 Proceedings of the Royal Society for 1877 (vol. xxvi. p. 488), 

 and were considered by them to show that light is inimical to 

 the development of bacteria in Pasteur's solution ; but that for 

 the full effect direct insolation is needed. Exposure to the sun's 

 rays, according to them, may simply retard development, or it 

 may completely sterilise the solution, by killing bacteria or their 

 germs contained in it. In a second paper read before the Royal 

 Society (Proceedings, vol. xxviii. p. 199), some further experiments 

 were detailed, which, however, did not, I venture to think, do 

 much towards settling the difficulties of the question. In the 

 same volume of the Proceedings (p. 212) Prof. Tyndall supplied 

 observations of his own, which confirmed the aonclusions of 

 Messrs. Downes and Blunt, in so far as the retardation of de- 

 velopment was concerned, but differed on the point of sterilisa- 

 tion by bacterial destruction being attainable by insolation. At 

 the last meeting of the British Association, Prof. Tyndall re- 

 turned to the subject (Nature, September 15, 18S1), and 

 related some further experiments confirming what he had 

 previously stated. 



I have recendy made a considerable series of experiments, 

 with the hope that under our bright Australian sun I might get 

 results decisive on the point of difference between these inquirers 

 and also confirming or negativing the result on which they were 

 agreed. I made use of Cohn's solution as the cultivation fluid 

 and common one-ounce phials as the vessels. The solution was 

 inoculated with a small quantity of fluid swarming with bacteria 

 (B. te, mo), the bottles plugged with cotton wadding and exposed 

 fully to the sun. Some of the experiments were made in the 

 hottest weather of February and March, and the later in April. 

 To begin with, I simply placed the bottles on the outside of a 

 window-sill, on which the sun shone during the greater part of 

 the day, a temperature of 124' F. being noted on one occasion, 

 and that probably not the highest reached. My first results 

 seemed fully to confirm the conclusions of Messrs. Downes and 

 Blunt, complete sterilisation apparently being sometimes attained, 

 at least as far as bacterial growth was concerned, the destruction 

 of mould spores, as also noted by them, not being so easily 

 accomplished. Suspecting at last that the effect might possibly 

 be due as much to elevation of temperature as to any special 

 chemical or other action of the sun s rays, I varied my pro- 

 cedure. I was led to do this in part by the circumstance that I 

 had not seen diffused light check in any way the bacterial 

 growth, when the solution exposed to it was kept at the same 

 temperature approximately as that in other bottles closely 

 wrapped in brown paper. It did happen, indeed, that the 

 exposed solution became opalescent sooner than that which had 

 been guarded. The method ultimately adopted was, to suspend 



the bottle outside of a window, and the particulars of one experi- 

 ment will make clear what resulted, and show the general 

 method. On April 6, at 2 p.m., the weather being bright but 

 cool, these bottles, containing each two drachms of inoculated 

 solution, were suspended outside of a window. The 7th was 

 cloudy, the 8th bright and cool ; and on the 9th, which was 

 bright and warm, all were still found transparent, and, at 9 a.m., 

 one was brought in out of the sun. On the 10th, which was 

 also bright, another was taken in at 9 a.m., the one which was 

 left out showing, at that time, faint signs of cloudiness. A 

 thermometer hung up beside it marked a temperature of 98" F. 

 Next day, the nth, at 9 a.m., the exposed solution was quite 

 milky, the others just beginning to show traces of opalescence, 

 the one removed on the 9th being least advanced. This experi- 

 ment, even by itself, was almost decisive. It established the 

 fact that insolation by itself does not prevent the growth of 

 bacteria in a perfectly transparent medium, and does not even 

 retard it, relatively to the time needed in solution less exposed, 

 but kept at a rather lower tempeiature. In another experiment 

 I found two bottles continuou^y exposed to the sun during two 

 bright dnys, become milky, the bacterial growth, in fact, only 

 beginning then, no trace of cloudiness having shown itself during 

 five previous days which were dark and cold. 



The conclusion I came to of necessity was, that the bacterial 

 development was mainly, if not wholly, dependent on tempera- 

 ture. On referring to a paper by Dr. Ed. Eidam, in Cohn's 

 Beitrage zur Biologic der Pfianzen, Heft iii., I found that he had 

 proved that the bacterium termo passes into a torpid condition 

 (Wiirmestarre), when exposed to a temperature of between 40° 

 and 45 C. (I04°-H3° F.) ; is killed by seven days exposure at 

 45° C, by fourteen hours at 47° C. (116° 3 F.), by three to four 

 hours at 5o*-52° C. (I22°-I25'6° F.), and by one hour at 60° C. 

 (140° F.). In this country there need be no difficulty in getting 

 a heat in the sun, greater than even the highest of these ; and I 

 should think it possible enough in England, on a hot summer 

 day, to get a temperature in exposed situations considerably over 

 104° F., sufficient to paralyse the bacteria, or even to kill them, 

 if the exposure was long enough continued. Any explanation 

 of the difference between the results of Messrs. Downes and 

 Blunt, and those of Prof. Tyndall, on the point of complete 

 sterilisation, is simply that, while they used small test-tubes, his 

 solutions were contained in flasks, and that the larger body of 

 fluid less easily reached the highest temperature attainable under 

 the conditions. The different results, with very small and larger 

 tubes, observed by the former, and to them evidently inexpli- 

 cable, if not simply accidental, is best explained on the same 

 principle. 



It is true that Prof. Tyndall agrees with the other inquirers in 

 disclaiming the notion that the apparently inimical influence of 

 light can be ascribed to difference of temperature ; but it is 

 evident that it had not occurred to them, that any possible eleva- 

 tion of temperature could act otherwise than by favouring bacte- 

 rial growth and multiplication. This is plain, from the words 

 used by Messrs. Downes and Blunt (Proceedings, vol. xxvi. p. 

 491), when, trying to account for some anomaly, they remark 

 that "external conditions — notably temperature — may retard or 

 counteract the preservative quality of the solar rays. It must 

 be understood, however, that the putrefactive tendency of warmth 

 does not, in our experience, with this solution at least, override 

 what we termed the preservative quality of light ; for, provided 

 that there was the full amount of sunlight, we have preserved 

 tubes exposed continuously from day to day as readily in hot 

 weather as in cool." Prof. Tyndall, in his recent paper, speaks 

 of his flasks having been exposed to strong sunshine for a whole 

 summer's day ; and, with reference to the more rapid occurrence 

 of turbidity in those which had been shaded, adds: "This 

 result is not due to mere difference of temperature between the 

 infusions. On many occasions the temperature of the exposed 

 flasks was far more favourable to the development of life than 

 that of the shaded ones." 



I feel the boldness of criticising the conclusions aimed at by 

 such a famous investigator as Tyndall, and all the more when 

 these are in accord, in the main, with those of other inquirers, 

 the joint results having hitherto, to all appearance, been accepted 

 as unimpeachable. I do so only after careful observation and 

 consideration, and with the hope that further investigations, made 

 with due precautions, will establish the correctness of what I 

 have here stated. My researches in detail will be brought before 

 the Royal Society of Victoria at the next meeting, and I will 

 take the liberty of forwarding you a copy of the paper when 



