March 15, 1894] 



NATURE 



467 



and consequently correspondent to that of the above-mentioned 

 cylinder of plaster, increased in weight, in an atmosphere 

 saturated with aqueous vapour, by only 3 '5 mgr. in twenty-four 

 hours. 



If we argue that the hygroscopicity is the cause of the 

 curvatures, we might assume that PhycoJiiyces is only affected 

 by bodies which absorb very little water, and that the above- 

 mentioned bodies, which are without effect on Phycomyccs, are 

 too strongly hygroscopic. But then a positive curvature ought 

 to be seen, at a certain distance from the bodies, where the 

 hygroscopic efTect is weaker ; and this is by no means the 

 case. 



With all these facts in view, I cannot agree with Errera's 

 hypothesis that the attracting effect of iron depends on a kind 

 of hydrotropism. According to the statement of Errera, many 

 hygroscopic bodies attract the hyphje, but it is hardly to be 

 presumed that this is actually owing to hygroscopicity, as other 

 hygroscopic bodies are without effect. It seems to me that 

 this i-; a case of radiation, depending on the molecular state of 

 the body, and manifesting itself by the physiological effect. 



In one point Errera corrects my statements as to the effect of 

 iron. I had found that the condition of the surface (burnished, 

 roughly brightened, or somewhat rusty) did not affect the re- 

 sults. Errera says that the effect of burnished steel is very 

 slight, and this I can confirm as regards very well burnished 

 steel. In this circumstance Errera finds a confirmation of his 

 hypothesis, since a burnished surface gets rusty, i.e absorbs 

 water veryslovly. In my opinion this fact only implies that 

 the state of the surface is of a certain importance for the radia- 

 tion in question, as is known to be the case with regard to the 

 radiation of heat and light. 



It is self-evident that my idea of this phenomenon, as depen- 

 dent on molecular vibration, is a mere hypothesis. It is, how- 

 ever, somewhat confirmed by the fact that similar physiological 

 effects are produced 'y some phenomena, which we must, from 

 the present siand-point of scie"nce, declare to be molecular 

 vibrations ; and the statement of this fact is the principal object 

 of this paper. 



Platinum belongs to the inactive metals, and well-burnished 

 steel has, as mentioned above, a very slight effect. Bat if ex- 

 posed for some time to direct sunlight, these bodies becime 

 active, i.e. the sunlight creates in them a condition which, 

 though otherwise imperceptible, manifests itself by the fact that 

 the body, clearly and even powerfully, attracts Phycomyccs. 

 The power of attraction appears on the illuminated as well as 

 on the op osite side of the body. This condition of the body 

 lasts for a few hours, but afterwards ceases. 



This phenomenon is somewhat mysterious. It is indeed as- 

 tonishing to see how the same piece of platinum-foil, which 

 during a series of experiments was without effect on our 

 Phycomyces, will attract them after being exposed to the sun, 

 without undergoing any outward change. 



But thi- phenomenon is not entirely without analogy. 

 It is a well-known fact that a number of nonluminous bodies 

 after being exposed to illumination emit light in a manner which 

 ■has been described as phosphorescence. Some bodies phospho- 

 Tasce only for fractions of a second, others for more than twenty- 

 four hours. Metals do not belong to the phosphorescing bodies, 

 but in the present case a kind of phosphoresence seems to take 

 place which is not perceptible to our eyes, but, on the other 

 hand, is effective on Phycomyces. The phenomenon might be 

 designated as dark phosphorescence. 



It is interesting to note that E. Becquerel, who thoroughly 

 ■studied the phenomena of phosphorescence, had foreseen some- 

 thing of the kind. He says ("La lumiere, ses causes et ses 

 ■effets," 1867, i. p. 259): " Meme si les corps ne sont pas 

 lumineux dans le phosphoroscope, on ne peut dire qu'il n'existe 

 aucun effet apres Taction du rayonnement ; car la lumiere pour- 

 rait exciter des vibrations d'une autre vitesse que celles qui sont 

 perceptibles a nos yeux (et en general plus lentes), et capables 

 de donner lieu soit a des effets de chaleur, soit a d'autres actions 

 imoleculaires encore inconnues. " 



With regard to the requisite intensity of light, I need only state 

 that in August intense sunlight during seventy minutes was 

 sufficient to cause activity, whereas an exposition of five hours in 

 .cloudy weather was without effect. I have not found out the 

 shortest effective period of the insola'ion ; and as to the duration 

 of the state induced by light, I can only say that bodies activated 

 in the afternoon, which, on being tested at once, caused 

 .curvatures in three to four hours, were without effect the next 

 piorning. 



NO, 1272, VOL. 49] 



That the effect is due to light, not to heat, is proved by 

 experiments in which the steel and pLuinum plates we-e heated 

 for hours to the temperature (4o'-45 ) iniicated by the ther- 

 mometers during the insolation. 



That the ultra-violet rays of the sun have no particular 

 share in the phenomenon, is proved by (he fact that the light 

 which has passed through a solution of quinine-sulphate activates 

 the respective bodies. 



In experimenting with other metals, and variou; non-phos- 

 phorescing bodies, I could not demonstrate with certainty any 

 such activation by light, which fact, however, does not exclude 

 the possible occurrence of a dark phosphorescence of too short 

 a duration to cause a physiological reaction. 



Finally, I have to mention that certain bodies are rendered active 

 by heat. I have found zinc to be one of them. Having heated 

 a stick of zinc (5 mm. in diameter) in a blow-pipe flame until 

 it began to melt, and having then allowed it to cool down 

 to the temperature of my hani. I got, after an experi- 

 ment of a few hours, the most beautiful curvatures in Phy- 

 comyccs I could wish for. After cooling down for several hours, 

 the stick was no longer active in this manner. Here we can 

 justly speak of positive thermotropism, which is all the more in- 

 teresting, as Wortmann in his experiments {Botanische Zcitimg, 

 18S3, p. 462) found only negative thermotropism in Phycomyccs. 



Some other bodies are quite different from zinc. The same 

 plate of platinum that was rendered active by an hour's insola- 

 tion, remained, after being heated red-hot for five minute*^, 

 just as inactive as before. Also in copper, cobalt, nickel, 

 tin, lead, and glass, no effect was to be produced by great 

 heat. There is not the slightest doubt but that plants, ia 

 their thermotropic curvatures, are affected by vibrations issuing 

 from the molecules of the body applied, and this is also veiy 

 likely the case with regard to the eff ct of light. It therefore 

 does not seem unjustifiable to assuine that even molecular vibra- 

 tions, which are inherent in the bodies themselves, or connected 

 with some change that they undergo, may cause si nilar physio- 

 logical effects. Fredrik Elfving. 



THE NEW IODINE BASES. 



"PURTHER details are given in the latest Berichle, by Prof. 

 Victor Meyer and Dr. Hartmann, concerning their recently- 

 discovered basic compounds of iodine. It will be remembered that 

 the fundamental base from which these new substituted bases are 

 derived is the hypothetical compound HO. IHo, and that the 



derivative HO.K 



X«H 



I 3 had been isolated as a strongly al- 



kaline substance readily soluble in water, and which forms salts 

 with acids with elimination of water, exictly like ammonium 

 hydroxide. For the parent substance, therefore, the name 

 iodonium hydroxide is proposed. At the conclusion of their 

 first paper, Prof Meyer and Dr. Hartmann announced that 

 they had just succeeded in isolating the simpler di-phenyl 

 derivative OH. I (CuH.j)^, and the present communication de- 

 scribes the strange mode of its genesis, and the character of the 

 free V.ase and its salts. The beautifully crystalline iodide was 

 frequently obtained in small quantities during the whole course 

 of I'rof. Meyer's work with iodoso-benzene. It was observed that 

 methyl iodide acts with great ener4y at the ordinary tempera- 

 ture U[)on the latter compound, and the product yields in con' act 

 with m )ist silver oxide a liquid from which potassium iodide 

 precipitates cry-tals of the new iodide, I.I (Ci-.Hg)^. It was 

 .subsequently found that when iodoso-benzene itself is triturated 

 with moist silver oxide, the filtered liquid likewise yields similar 

 crystals of diphenyl-iodonium iodide upon the addition of pot- 

 assium iodide. This discovery led to a systematic study of the 

 conditions of the reaction, and it was eventually elicited that 

 freshly- prepared iodoso-benzene is incapable of so acting, but 

 that by a few days' exposure in a thin layer to daylight, or, 

 better still, by heating for some hours to 60°, it is rendered 

 capable of producing the new base when brought in contact 

 with oxide of silver. Moreover, it was ascertained that po'.ash 

 or soda are likewise capable of bringing about the change, 

 although owing to subsidiary decompositions, not so advantage- 

 ously as moist oxide of silver. It has finally been proved hat 

 the reaction depends upon the fact that upon healing to 60' or 

 exposure to sunlight iodoso-benzene, C^Hj 10, is partially con- 

 verted in'o the more highly oxidised compound Cgllj.IO.^, and 

 by the action of moist silver oxide upon the mix'ure of the two 



