September 6, 1894J 



NA TURE ^ 



46- 



limb accompanied the depressor excitation because the dilator 

 supply wa^s cut off. 



Prof. Waymouih Reid gave an account of the alteration in 

 ihe mucous membrane of the lateral pouches of the pigeon's 

 crop, which were associated wiih the breeding season of the 

 bird, and resulted in the formation of masses of f*t-holding 

 material constiluting the so-called pfgion's milk. The secre- 

 tion of this material is in its histological features analogous to 

 ihe formation of sebum in the sebaceous glands, the fat being 

 contained in cells which are cast ofT in masses from the mucous 

 surface. The material is used for feeding the young pigeon, 

 and when analysed is found to contain from 7 to 9 pe- cent of 

 fat and 12 to 15 percent, of proteids, the chief of which is a 

 nucleo-albumin ; unlike true milk it coniains na sugar, but 

 among its proteids is a caseinogen which clots with rennet with 

 or without the addition of calcic chloride. 



Prof. Dubois read a paper on the production of heat in 

 hybernating animals, and brought forward the results of ex- 

 p;riments made on the marmot in order to ascertain what 

 CTCumstances influence the change which lakes place at the end 

 of hybernation. Section of the cord at the level of the fourth 

 cervical nerve interferes with the waking from winter sleep, the 

 delay thus caused being only partially due to the muscular 

 paralysis and consequent inability to produce heat, since it 

 appears that the integrity of the sympathetic system is an 

 essential factor in the process. Further experiments ocemed to 

 indicate that the nervous control of the circulation was neces- 

 sary for the waking up, and that the most important part of the 

 circulation was that through the liver, which under the condi- 

 tions produced by the section was inadequate for the supply of 

 that organ. In consequence of this inadequate circulation the 

 author believed that the proper functions of the liver were very 

 much interfered with, and that in the normal animal these 

 functions were at the moment of waking very actively carried 

 on, particularly those by which glycogen is converted into 

 sugar. 



Prof. Ilaycraft showed some micro-photographs of collodion 

 casts of muscle fibres in which the transverse stri.-e of the 

 fibres were displayed. This communication was followed by 

 one from Prof. Rutherford, who exhibited on the screen 

 micro-photographs of muscle fibres both at rest and in con- 

 traction. /^.9SA<-'^J — 



Tuesday.— K combined meeting of the Physical and Physio- 

 logical Sections was held in the large theatre of the museum, 

 when Prof. Lodge showed a number of experiments upon the 

 reflection, polarisation, and refraction of Hertz waves, using as 

 a detector for the presence of the propagated electrical disturb- 

 ance an extremely sensitive cohesion tube. This contained 

 fine particles in imperfect contact, and consequently oliering 

 considerable resistance to the passage of an electric current. 

 The surging in the particles of an electric disturlianci causes a 

 better contact lo be established, and the resistance consequently 

 to be enormously diminished. Prof. Lodge followed thisdemon- 

 stration with a suggestion as to the mode in which it was 

 possible to conceive of a reaction of the retinal structures to 

 light vibrations. If we assume that the retinal elements con- 

 stitute an imperfect conductor, and that a constant eleclro- 

 I motive source is present in the retinal tissues, then it is not 

 improbable that the light waves would cause a sudden diminution 

 in the resistance of the elements, .and allow the passage of a 

 previously masked current ; this current might excite the 

 nerve-endings, and thus start the necessary nerve impulses. He 

 pointed out that Ihe coherer was acted on not only by the 

 sudden commencement, but also by the sudden cessation, of 

 the Hertz waves, and drew attention to Hering's view th.at 

 white and black are both positive sensations, and both caused 

 by retinal excitation. He stated that as regards colour, mathe- 

 maticians only demanded a triple starting-point, and that since 

 in Hering's theory three such independent factors were 

 postulated, no objections to this theory could be raised on that 

 score. The Young- Ilelmholtz theory seemed to him difficult 

 to reconcile with the f.acts described by physiologists and ob- 

 served by himself. 



A discussion followed, in which several physiologists took 

 part, the general tendency of the tone being that the suggestion 

 must be capable of being applied 10 all living electromotive 

 structures which display electrical changes when called into 

 activity. It was also pointed out that Ihe histological appear- 

 ances were not at any rate opposed to Prof. Lodge's suggestion. 

 Prof. Osborn described a modification of Golgi's method used 



NO. I2Q7, VOL. 50] 



by Mr. Strong, of New York, and showed beautiful photographs 

 of nerve cells from various parts of the central nervous system 

 treated in this way. 



Dr. H ddane brought before Ihe Section the evidence which 

 had led him to the conclusion that in the recent colliery ex- 

 plo4on in .South Wales, and probably in most previous ones, 

 the cause of death by suffocation was the deficiency of oxygen 

 in the mine due lo its displacement by Ihe products of the 

 explosion, i.e. afier-damp. Suffocation by deficiency of oxygen 

 occurs when the respired air contains less than 8 per cent, of 

 O ; it is ushered in by an extremely sudden attack of muscular 

 paralysis, so that there is but little warning of the danger when 

 air is inspired deficient in O, and little chance of escape owing 

 to the muscular failure. Suffocation through excess of CO., is 

 quite different, as it is preceded by gradual respiratory distress 

 in which the neuro-muscular system is aroused to greater 

 activity. In ad^iition to the deficiency of O, the poisonous 

 "after-damp " contains often at least two noxious gases in fatal 

 percentage, these being CO and H.jS. The most effective 

 method of fighting one's way through after-damp seemed there- 

 fore to be one which aimed at restoring to the inspired air an 

 adequate quantity of oxygen, and this the author thought might 

 be effectually done by suitable portable cylinders of this gas. 



Mr. W. G. Smith brought forward some observations illus- 

 trating some of the mental conditions which influence the 

 association of ideas, i.e. memory. Experiments were made as 

 to the effect upon such association of contemporaneous nervous 

 activities other than those which presumably were more or less 

 directly involved. Thus the power of recollecting a given 

 arrangement of letters which had been exposed before Ihe eye 

 for ten seconds was found to be modified by the person under 

 observation having to carry out simultaneously any one of the 

 following among other operations during the period of ex- 

 posure : tapping rhythmically on the table with the forefinger; 

 speaking a simple syllable over and over again ; carrying out a 

 simple sum in addition in an audible voice. In all cases the 

 effect was to confuse the recollection, the degree of confusion 

 being greatest in the last two described instances. 



Wednesday Morning. — Profs. G.itch and Lodge demonstrated 

 the method employed by them in order to study the physiological 

 effects produced by rapidly alternating currents of high intensity. 

 They first showed that a nerve muscle preparation from thefrc^, 

 if held in the neighbourhood of a friction machine lo the poles 

 I of which were attached Leyden jars, responded by a single con- 

 traction whenever a spaik passed between the knobs of the 

 m.achine. Since there was no connection, except an air one, 

 between the preparation ami the machine, it was evident that 

 the response was due to the preparation being in the line of 

 force which spreads out from the knobs, and that when the spark 

 passed, the sudden equalisation of these effects must be accom- 

 panied by a surging to and fro in the exposed nerve ; the 

 sudden character of this excites the tissue. They then showed 

 the following experiment : — 



A looped circuit was arranged connecting the two Leyden 

 jars together, but leaving them attached to the friction machine ; 

 the end of the loop w.is connected to the earth, this being 

 essential to avoid all static effects. Two wires were joined, one 

 to each side of the loop, and the ends placed so as to embrace 

 the exposed nerve of a nerve muscle preparation midway be- 

 tween the central end and the mu.scle. The upper end of the 

 nerve was now brought into contact by means of other separate 

 electrodes with an induction apparatus, and was excited every 

 four seconds by a minimal excitation. On working the friction 

 machine, and pas>ingthestrong rapidly-oscillating currents of the 

 Leyden jars through the preparation, it was observed that only 

 when the spark of the friction machine was extremely intense did 

 the preparation respond by a contraction to these rapidly alter- 

 nating currents, and that the sole effect of rather feebleralternating 

 currents was to so alter the nerve that it ceased for a brief period 

 to transmit the nerve impulse evolved by the constant rhythmical 

 stimulus at the central end. The passage of these currents thus 

 seems to produce a temporary paralysis of the nerve without 

 causing excitation, acting thus like pressure or cold. 



Prof. Engelmann described a new kymograph and poly- 

 rheotome, and exhibited tracings obtained with the instrument, 

 which showed the great accuracy of the app.iralus. The record- 

 ing surface was driven by means of a weight which was so 

 contrived as to ensure that in each experiment the same 

 velocity should be reached before the weight ceased lo act, and 

 the subsequent revolution rendered practically uniform. 



