September 9, 1922] 



NA TURE 



343 



terms "-Vital energy " or " biotic energy." To 

 narrow the problem, let us in the meantime exclude 

 " vital " energy altogether, since, as an expression, 

 it must include nerve-energy. 



Now it is well known that one or two writers have, 

 years ago, stated their belief in the reality of nerve- 

 energy ; of such are Sir William Hale White and 

 Prof. Macdougall, then of Oxford, now of Harvard. 

 Dr. Hale White in 1886 (Lancet, July 24) suggested 

 the term " neurorheuma," and Macdougall in 1903 

 " neurine " for just the same thing as is understood 

 by " nerve-energy." These terms were introduced 

 to supply suitable technical terms (in place of the 

 popular " nerve-energy ") to designate a reality 

 among the other forms of energy. Macdougall's term 

 " neurine " has not been more readily adopted, 

 because he associated it with a theory of inhibition 

 which has occasioned much criticism. 



Adopting for the moment Hale White's "neuro- 

 rheuma," it means " flow in a nerve." But flow of 

 what ? Surely of nerve-energy. Some physiologists 

 would not sav so : they would reply — flow of nerve- 

 impulses. Naturally, for nerve-impulses are the only 

 things which do or can flow in nerves. Now nerve- 

 impulses are real, and as they are the only things 

 which flow in nerves, and nerve-energy is in nerves ; 

 then nerve-energy is but a synonym for nerve-impulses. 

 This is exactly what Dr. White intended, for he 

 insisted that nerve-energy was but one kind of energy 

 amid several other kinds, heat, light, electricity, 

 etc. 



In itself nerve-energy is clearly sui generis, because 

 the neurons (nerve cells and fibres) to which it is 

 exclusively related are themselves histologically sui 

 generis. 



Now no one would teach that the nerve-fibres are 

 the sources of the impulses they transmit ; it is the 

 cell-bodies which alone can be dynamogenic. The 

 problem of the transmutation of nerve-energy into 

 some other form of energy must in the meantime be 

 left unattacked. 



If energy there be, the cells are the only sources 

 transmitting it to the fibres. Nerve-energy must 

 be capable of existing both in the potential and 

 kinetic states. Such indeed seems to be the truth, 

 for it may be regarded as potential in the cells and 

 kinetic in the fibres. But in the last analysis, what 

 is this potential energy but that liberated by the 

 metabolism of the nerve-cell, one aspect of the 

 oxidations and reductions going on there ? No 

 physiologist would deny the reality of the existence 

 of this fundamentally chemical energy of the neurone ; 

 but what is it if it is not nerve-energy ? 



Nerve-impulses (nerve-energy) being sui generis 

 must make their measurement very difficult, if not 

 impossible, except in terms of some other form of 

 energy. 



Now the most measurable thing which nerve- 

 impulses do is to produce electric current. Why is 

 the E.M.F. of this current not a sufficiently good 

 measure of nerve-energy ? It is sometimes assumed 

 that we can measure the intensity of nerve-impulses 

 by the muscular, cardiac, glandular, or other " work " 

 which they evoke. It is true that feeble innervation 

 will give rise to feeble muscular effort, violent 

 to violent. But caution is necessary in drawing 

 deductions as to the potential of the feeble and 

 violent innervations respectively. 



The feeble muscular effort may be feeble because 

 only a few muscular fibres are excited, the strong 

 because many ; and all the while the actual E.M.F. 

 of the nerve-impulses which excited the feeble effort 

 may be the same as that of those which excited the 

 violent. 



The violent neural antecedent may be one that, 



NO. 2758, VOL. 1 IO] 



involving many nerve-cells in the commotion, " fires 

 off " many muscle-fibres, while the feeble neural 

 antecedent involves few ; but the E.M.F. of the 

 nerve-impulses in both cases may be the same. The 

 work of Keith Lucas would lead us to this conclusion. 



But all this does not affect the doctrine of the 

 reality of nerve-energy. Nerve-energy is real although 

 its measurement is difficult and may be impossible. 

 We believed in the reality of animal heat, electricity, 

 and light long before we were able to measure these 

 by calorimeters, galvanometers, and photometers. 

 Nerve-impulses impinging on a muscle stir it to 

 activity or quell it to inactivity, so that they must be 

 at least as real as the muscular energy excited or 

 quelled respectively. Similarly nerve-impulses im- 

 pinging on a nerve-cell cause it to transmute its 

 potential nerve-energy into nerve-impulses. 



Contrary to what the phrase would imply, Miiller's 

 " specific nerve-energy " does not throw any light 

 on our problem. The phrase is antiquated though it 

 embodies an important truth. What Miiller had in 

 mind was the oneness of the central result with the 

 many forms of the peripheral stimulation. 



Unless nerve-energy is a reality, neurasthenia 

 becomes meaningless. Now although the term 

 " neurasthenia" may not connote a definite clinical 

 entity, yet fatigue of the nervous system both 

 in its acute and chronic forms is a fact. From a 

 priori considerations alone there must be fatigue 

 of neural origin as of any other. The partial solution 

 of the granules of Nissl has been asserted to be the 

 histological counterpart or basis of fatigue of neuro- 

 plasm, but whether or not this be correct, a state of 

 functional disability must be capable of being induced 

 in neurones. Surely fatigue means diminution of 

 some sort of energy : muscular fatigue is a reality, 

 why not neural? Physiologists doubt the "fatigue- 

 ability " of nerve-fibres which are but conductors, but 

 no neurologist doubts the " fatigueability " of nerve- 

 cells. This must, in other words, be nothing else 

 than the diminution of the potential and quantity of 

 the energy of neurones. All the following writers have 

 used the expression " nerve-energy " or " nerve-force " : 

 the late Dr. Hughlings Jackson, the late Dr. Clouston, 

 the late Sir William Osier, the late Dr. Weir Mitchell, 

 the late Dr. Frederick Taylor ; and of living writers, 

 Sir William Bayliss, Profs. Halliburton, Howell, and 

 Starling, and Sir Frederick Mott. 



In closing let me make one or two suggestions as to 

 how nerve-energy might be measured. 



1 . The increase of conductance in the skin under the 

 influence of descending nerve-impulses as measured 

 in the psycho-galvanic phenomenon (Waller, Golla). 



Surely the magnitude of this is causally related to 

 that of the antecedent nerve-energy liberated ? 



Even if this be proved to be a glandular phenomenon, 

 we have the essentials of quantitative estimation 

 in it. 



2. Measure the E.M.F. of the current of action, 

 say, in the cortical visual centre as the result of 

 feeble and of strong retinal stimulation respectively. 



3. Estimate the pressures or other stimuli necessary 

 to suppress certain reflexigenous tendencies. 



D. Fraser Harris. 

 Dalhousie University, Halifax, N.S. 



Noctiluca as an Enemy of the Oyster. 



In view of the serious problems which have of late 

 been engaging the attention of oyster culturists, 

 involving as they do the whole future of the industry, 

 and in connexion with which a considerable amount 

 of scientific investigation has been carried out, the 

 following preliminary note of observations made by 



