342 



NATURE 



[August ii, 1892 



Next year's meeting will be held at Nottingham, and 

 that for 1894 at Oxford. 



The list of awards finally arrived at was as follows: — 



Investigation of the Eruptive Deposits of Pentland Hills £10 



Isomeric Naphthalene Derivatives 20 



Index of Plants, &c 20 



Climatology,&c., of Africa ... ... ... ... ... 50 



Place Names in Scotland 10 



Electrical Measurements .. ... ... ... ... 25 



Observations on Ben Nevis ... ... ... ... ... 150 



Falmouth Observatory 25 



Photography of Meteorological Phenomena 10 



Solar Radiation 10 



Spectra of Elements ... ... ... ... ... ... 10 



Analyses of Iron and Steel ... ... ... ... ... 20 



Action of Light on Dyed Colours 5 



Erraiic Blocks of England, Wales, and Ireland 10 



Fossil Phyllopoda ... ... ... ... ... ... 5 



Geological Intervals ... ... ... ... ... ... 10 



Underground Waters... ... ... ... ... ... 5 



High-level Shell-bearing Deposits 20 



Zoological Station at Naples ... ... ... ... 100 



Plymouth Biological Station 30 



Sandwich Islands ... ... ... ... ... ... 100 



West Indies 50 



Irish Sea Exploration ... ... ... ... ... 30 



Oxygen in Asphyxia .. ... ... ... ... ... 20 



Exploration of the Karakorum Mountains .. ... 50 



Methods of Economic Training ... ... ... ... 5 



Anthropometric Tabulations ... 5 



Exploration of Assam ... ... ... ... ... 25 



North- West Tribes of Canada ... 100 



Natives of India ... ... ... . . ... ... 10 



Corresponding Societies Committee 30 



Total ... £910 



SECTION D. 



BIOLOGY. 



Opening Address by Prof. William Rutherford, M.D., 

 • •"-' F.R.S., President of the Sectiok, 



At the meeting of this Association held at Birmingham in 

 1886 I had the honour of delivering a lecture on the Sense of 

 Hearing, in which I criticized the current theory of tone-sensa- 

 tion, and I propose on this occasion to discuss the current theories 

 regarding our sense of colour. 



I may premise that our conceptions of the outer world are 

 entirely founded on the experience gathered from our sensory 

 impressions. Through our organs of sensation, mechanical, 

 chemical, and radiant energies impress our consciousness. The 

 manner in which the physical agents stimulate the peripheral 

 sense-organs, the nature of the movement transmitted through 

 our nerves to the centres for sensation in the brain, the manner 

 in which different qualities of sensation are there produced— all 

 these are problems of endless interest to the physiologist and 

 psychologist. 



Every psychologist has acknowledged the profound signifi- 

 cance of Johannes Miiller's law of the specific energies — or, as 

 we should rather say, the specific activities of the sense-organs. 

 To those unfamiliar with it, I may explain it by saying, that if a 

 motor nerve be stimulated, the obvious result is muscular move- 

 ment ; it matters not by what form of energy the nerve is stimu- 

 lated — it may be by electricity or heat, by a mechanical pinch 

 or a chemical stimulus, the specific result is muscular contrac- 

 tion. In like manner, when the nerve of sight is stimulated — 

 it may be by light falling on the retina, or by electricity, or 

 mechanical pressure, or by cutting the nerve — the invariable 

 result is a luminous sensation, because the impression is trans- 

 mitted to cells in the centre for vision in the brain, whose specific 

 function is to produce a sense of light. 



The same principle applies to the other sensory centres ; 

 when thrown into activity, they each produce a special kind of 

 sensation. The sun's rays falling on the skin induce a sense of 

 heat, but falling on the eye, they induce a sense of sight. In 

 both cases the physical agent is the same ; the difference of 

 result arises from specific differences of function in the brain 

 centres concerned in thermal and visual sense. We have no 



NO. I 189, VOL. 46] 



conception how It is that different kinds of sensation arise from 

 molecular movements in the different groups of sensory cells ; 

 we are as ignorant of that as we are of the nature of conscious- 

 ness itself. 



The subject I propose to discuss on this occasion is not the 

 cause of the different kinds of sensation proper to the different 

 sense-organs, but the causes of some qualities of sensation pro- 

 ducible through one and the same sense-organ. 



The theory of tone-sensation proposed by Helmholz is, that 

 the ear contains an elaborate series of nerve terminals capable 

 of responding to tones varying in pitch from 16 vibrations to 

 upwards of 40,000 vibrations per second, and that at least one 

 different fibre in the auditory nerve, and at least one different 

 cell in the centre for hearing, is affected by every tone of per- 

 ceptibly different pitch. Although the physical difference 

 between high and low tones is simply a difference in frequency 

 of the sound waves, that is not supposed by Helmholz to be 

 the cause of the different sensations of pitch. According to his 

 theory, the function of frequency of vibration is simply to excite 

 by sympathy different nerve terminals in the ear. The mole- 

 cular movement in all the nerve fibres is supposed to be iden- 

 tical, and the different sensations of pitch are ascribed to a 

 highly specialized condition of cells in the hearing centre, 

 whereby each cell, so to speak, produces the sensation of a tone 

 of definite pitch, which in no way depends on the frequency of 

 incoming nerve impulses, but simply on the specific activity of 

 the cell concerned. 



In my lecture on the Sense of Hearing I pointed out in detail 

 the great anatomical difficulties attending the theory in question. 

 I endeavoured to show the physical defect of a theory which 

 does not suppose that our sensations of harmony and discord 

 must immediately depend upon the numerical ratios of nerve 

 vibrations transmitted from the ear to the central organ, and I 

 offered a new theory of hearing based upon the analogy of the 

 telephone. According to that theory, there is probably no 

 analysis of sound in the ear ; the air-cells at the peripheral ends 

 of the auditory nerve are probably affected by every audible 

 sound of whatever pitch. When stimulated by sound they pro- 

 bably produce nerve vibration, simple or compound, whose 

 frequency, amplitude, and wave- form correspond tp those of the 

 sound received. The nerve vibrations arriving in the cells of 

 the auditory centre probably induce simple sensations of tones 

 of different pitch, or compound sensations of harmonies or dis- 

 cords strictly dependent on the relative frequencies of the nerve 

 vibrations coming in through the nerve. 



I cannot now recapitulate the evidence derived from anatomi- 

 cal, experimental, and pathological observations that give 

 support to my theory of hearing, but I may briefly say that it is 

 opposed to the theory of specific activities, in so far as it has 

 been applied to explain the different qualities of sound sensa- 

 tion. It is, however, in strict accord with the fundamental 

 proposition stated by Fechner^ in his great work on Psycho- 

 physics in these words : " The first, the fundamental hypothesis 

 is, that the activities in our nervous system on which the 

 sensations of light and sound functionally depend are, not less 

 than the light and sound themselves, to be regarded as depen- 

 dent on vibratory movements." It is evident that, if we could 

 only comprehend the nature of the molecular movement in the 

 nerve that links the vibration of the physical agent to that in 

 the sensory cell, we could advance towards a true theory of the 

 physiological basis of different qualities of sensation in the 

 different sense-organs. As yet no definite answer can be given 

 to the question, what sort of molecular movement constitutes a 

 nerve impulse, but in recent years our knowledge of the subject 

 has been extended in a direction that opens up a vista of new 

 possibilities. 



A nerve impulse travels at a rate not much more than 100 

 feet per second — an extremely slow speed compared with that 

 of electricity in a wire. It has been thought to be of the 

 nature of a chemical change sweeping along the nerve, but that 

 hypothesis is opposed by the fact that the most delicate thermo- 

 pile shows no production of heat, even when an impulse is 

 caused to sweep repeatedly along the same nerve. Again, 

 it is far easier to fatigue a muscle than a nerve. A living 

 frog's nerve removed from the animal, and therefore deprived 

 of all nutrition, can retain its excitability for nearly an hour, 

 although subjected all the while to thirty or forty stimulations 

 per second. An excised muscle, when similarly stimulated, 

 is exhausted far sooner, because the mechanical energy entirely 

 1 "Elementeder Psychopliysik," i86o 2ml edition, 1889, part ii. p. 282. 



