NoVE.MliER 22, 1894J 



NA JURE 



Cambridge. — Dr. Forsyth, F.K..S., has been appointeil 

 Chairman cjf=the Examiners for I'art II. of the Mathematical 

 Tripos. 



Mr. E. H. Ilankin, Fellow of St. John's College, and Pro- 

 fessor ol Bacteriology at .\s;ra, has been appointed lo represent 

 the University at the Indian Medical Congress to be held at 

 Calcutta in December. 



The following is the Syndicate appointed to consider a repoit 

 in the question of special encouragement, by new degrees or 

 'therwise, for post-yraduale study and research in the University : 

 Ihe Vice-chancellor, Dr. Maiiland, Dr. D. Macalitter, Dr. 

 Jebb, Dr. Forsyth, F.R.S., Prof Marshall, Prof. Gwatkin, 

 Prof. Foster, F.R.S., Prof. Thomson, F.R.S., Mr. A. \V. \V. 

 Dale, of Trinity Hall, and Mr. W. Bateson, F.R.S., of St. 

 John's College. 



A Grace authorising the Cavendish Laboratory Syndicate lo 

 obtain specifications and tenders for the proposed extension of 

 the Laboratory, was offered to the .Senate on November 22. 



SCIENTIFIC SERIALS 



American /ournal 0/ Siiiiicf, November. — On variations and 

 mutations, by W. B. Scott. The author discusses the problem 

 of animal morphology in its various aspects, and the different 

 lines along which a solution has been sought for. These are 

 that of comparative anatomy, embryology, and paU,;ontology, 

 to which, since Bateson's work on the study of variation, a 

 fourth has been joined. The author criticises in detail Bate- 

 son's method and its results, and comes to the conclusion that 

 we can no longer assume as a fundamental and self-evident 

 truth that individual variations are the material from which new 

 species are constructed. — Resonance analysis of alternating 

 currents, by M. J. Pupin. This analysis is performed by means 

 o( a " resonator circuit" consisting of an inertia coil, a rheostat 

 and a condenser in shunt with an electrostatic voltmeter. The 

 capacity of the condenser is gradually increased from zero 

 upwards. Whenever a capacity has been reached, which with 

 the self induction of the resonator circuit produces resonance 

 with one of the harmonics in the main circuit, then the reson- 

 ant rise of potential produces a large deflection in the voltmeter. 

 In this manner all the harmonics which are present in the 

 current of the main circuit can be detected in a few minutes. — 

 On some new methods of obtaining platinochlorides, and on 

 the probable existence of a platinum subchloride, by .M. Carey 

 Lea. One of the new methods employs potassium acid 

 sulphite, with a solution of which potassium platinic chloride 

 is moderately heated. The reduction takes about ten to twelve 

 liours, and is known to be complete when the solution has 

 a pure red colour free from yellow. The second method is 

 that with alkaline hypophosphites. If in obtaining potas- 

 sium platinochloride with the aid of a hypophosphile in 

 excess, the heat is continued after complete conversion to the 

 red salt, the solution in a few minutes changes from red 

 :o dark brown. The substance which gives the solution this 

 dark brown colour is very deliquescent, and cannot be crystal- 

 lised. It cannot be completely separated from the other 

 substances in solution. The author is led by its reactions to 

 suspect that it is a subchloride of platinum, analogous to that of 

 silver. 



lounial of Anatomy and Physioh\^y, October. — Dr. 

 Gustav Mann, in a paper entitled "Histological Changes 

 induced in Sympathetic, Motor and Sensory Nerve Cells 

 by Functional .\ctivity (preliminary note)," gives an .iccount 

 of experiments made by him to test the observations of 

 Hodge and F. Vas. Dr. Mann's observations relate to 

 the cervical symp.ilhetic ganglia (which also formed the 

 subject of F. Vas's investigations), the motor area of the 

 cerebrum, and to the retina and optic centres of the brain. His 

 results in part agree with thise of Hodge, in part with those of 

 Vas, but they also in other particulars go beyond both. He 

 considers that he has placed beyond doubt, that: (i) During 

 rest, several chromatic materials are stored up in the nerve cell, 

 ■ind that these materials are used up by it during the perform- 

 ance of its function. (2) .Activity is accompanied by an in- 

 crease in ^ize of the cells, the nuclei, and the nucleoli of 

 sympathetic, ordinary motor and sensory ganglionic cells. (3) 

 Fatigue of the nerve cell is accompanied by shrivelling of the 

 nucleus, and probably also of the cell, and by the formation of a 

 diffuse chromatic material in the nucleus. 



NO. 1308, VOL 51] 



SOCIETIES AND ACADEMIES 

 London. 



Royal Society, November 15. — " On the Ascent of Sap." 

 By Henry H, Dixon, .-Assistant to the Professor of Botany, 

 Trinity College, Dublin, and Dr. J. Joly, F.R.S. 



Slrasburger's experiments have eliminated the direct action of 

 living protoplasm from the problem of the ascent of sap, and 

 have left only the tracheal tissue, as an organised structure, and 

 th e transpiration-activity of the leaf wherein to seek an explana- 

 tion of the phenomenon. The authors investigate the cap- 

 abdity of the leaf to transpire against excessive atmospheric 

 pressures. In these experiments the leaf was found able to 

 bring forward its water meniscuses against the highest pressures 

 attained and freely transpire. Whether the draught upon the 

 sap established at the leaf during transpiration be regarded as 

 purely capillary or not, these experiments lead the authors to 

 believe that it alone is quite inadequate to effect the elevation by 

 direct tension of the sap in tall trees. Explanations of the 

 lifting of the sap from other causes prove inadequate. 



K reconsideration of the principal experiments of previous 

 observers and some new experiments of the authors lead to the 

 view that the ascent is principally in the lumen and not in the 

 wall. 



The explanation of how the tensile stress is transmitted in the 

 ascending sap without rupture of the coluinn of liquid is found 

 in the stable condition of this liquid. The stale of stability 

 arises from two circumstances : the internal stability of a liquid 

 when mechanically stretched, whether containing dissolved 

 gases or not, and the additional stability conferred by the 

 minutely subdivided structure of the conducting tissue, which 

 renders the stressed liquid stable even in the presence of free 

 gas. 



By direct experiments upon water containing large quantities 

 of dissolved air, the state of internal stability is investigated 

 And, further, by sealing up in the vessels, in which the water to be 

 put under tension is contained, chips of the wood of Taxus 

 Inucata, the authors find that their presence in no case gives 

 rise to rupture of the stressed liquid, but that this occurs prefer- 

 ably anywhere else, and usually on the gl.oss walls. The estab- 

 lishment of tensile stress is effected in the usual way, by cooling 

 the completely filled vessel. A measurement possessing con- 

 siderable accuracy afforded '\ atmospheres as being attained in 

 some of the experiments. 



The second condition of stability arises directly from the 

 property of the pit-membranes to oppose the passage of free 

 gas, while they are freely permeable to the motion ol a liquid. 

 Hence a chance development of free gas is confined in effect 

 to the minute dimensions of the compartment in which it is 

 evolved, and this one lumen alone is rendered for the time being 

 non-conducting. On the other hand, in the water-filled portion 

 of the tiacheal tissue, the closing membranes, occupying the 

 median and least obstructive position, the motion of the stress 

 sap is freely allowed. The structure of the conducting tissue 

 is, in fact, a configuration conferring stability on a stressed 

 liquid in I the' presence (from various causes) of free gas. 

 .\s neither free gas nor unwetted dust particles can 

 ascend with the sap, the authors contend that the state of 

 tensile stress necessary to their hypothesis is inevitably induced. 



The energy relations of the leaf with its surroundings, on the 

 assumption that evaporation at capillary water-surfaces is 

 mainly responsible for the elevation of sap, may be illustrated 

 by the well-known power of the water-filled porous pot to 

 draw up mercury in a tube to which it is sealed. The authors 

 describe an engine in which the energy entering in the form of 

 heat at the capillary surfaces may be in part utilised to do 

 mechanical work : a battery of twelve small porous pots, freely 

 exposed to the air, keeping up the continuous rotation of a fly- 

 wheel. Replacing the porous pots by a transpiring branch, 

 this too maintains the wheel in rotation. This is, in fact, a 

 veget.nble engine. In shoit, the transpiration effects going on 

 at the leaf are, in so far as they are the result of spontaneous 

 evaporation and uninfluenced by other physiological phenomena, 

 of the "sorting demon " class, in which the evaporating surface 

 pl.ays the part of a sink of thermal energy. 



If the tensile stress in the sap is transmitted to the root, the 

 authors suggest that this will establish in the capillaries of the 

 root surface meniscuses competent to condense water rapidly 

 from the surrounding soil. They show by experiment the power 

 possessed even by a root injured by lifting from the soil, of con- 

 densing water vapour from a damp atmosphere. Such a state 



