754 TRANSACTIONS OF SECTION t. 



or adsorption of potassium salts in or along the course of the axon, while the 

 nerve cell itself is very largely free from them, can have but one explanation on 

 the basis of the Gibbs-Thomson principle, and that explanation is that surface 

 tension on the nerve cell itself must be high while it is low on or in its axon. 



The conclusions that follow from this are not far to seek. We know that an 

 tlectrical displacement or disturbance of ever so slight a character occurring at 

 a point on the surface of a drop lowers correspondingly the surface tension at 

 that point. What a nerve impulse fundamentally involves we are not certain, 

 but we do know that it is always accompanied by, if not constituted of, a change 

 of electrical potential, which is as rapidly transmitted as is the impulse. When 

 this change of potential is transmitted along an axon through its synaptic ter- 

 minals to another nerve cell, the surface tension of the latter must be lowered 

 to a decree corresponding to the magnitude of the electrical disturbance pro- 

 duced, and, in consequence, a slight displacement of the potassium ions would 

 occur at each point in succession along the course of its axon. This displace- 

 ment of the ions as it proceeded would produce a change of electrical potential, 

 and thus account for the current of action. The displacement of the ions in the 

 axon would last as long as the alteration of surface tension which gave rise to it, 

 and this would comprehend not more than a very minute fraction of a second. 

 Consequently, many such variations in the surface tension of the body of the 

 nerve cell would occur in a second; and, as the physical change concerned would 

 involve only the very surface layer of the cell, a minimum of fatigue would result 

 in the cell, while little or none would develop in the axon. 



It may be pointed out that in medullated nerve fibres the lipoid-holding 

 sheath, in close contact as it is with the axon, must of necessity maintain on 

 the course of the latter a surface tension low as compared with that on the nerve 

 cell itself, which, as the synaptic relations of other nerve cells with it postulate, 

 is not closely invested with an enveloping membrane. In non-medullated nerve 

 fibres the simple enveloping sheath may function in the same manner, and 

 probably, if it is not rich in lipoid material, in a lees marked degree. 



What further is involved in all this, what other conclusions follow from 

 these observations, I must leave unexplained. It suffices that I have indicated 

 the main points of the subject, the philosophical significance of which will appear 

 to those who will pursue it beyond the point where I leave it. 



In bringing this address to a close I am well aware of the fact that my 

 treatment of the subjects discussed has not been as adequate as their character 

 would warrant. The position which I occupy imposes limits, and there enters 

 also the personal factor to account in part for the failure to achieve the result 

 at which I aimed. But there is, besides, the idea that in applying the laws of 

 surface tension in the explanation of vital phenomena I am proceeding along a 

 path into the unknown which has been as yet only in a most general way 

 marked out by pioneer investigators, and in consequence, to avoid mjstakes, I 

 have been constrained to exercise caution, and to repress the desire to make larger 

 ventures from the imperfectly beaten main road. Perhaps, after all, I may 

 have fallen into error, and I must therefore be pi'epared to recall or to revise 

 some of the views which I have advanced here, should they ultimately be found 

 wanting. That, however, as I reassure myself, is the true attitude to take. It 

 ia a far cry to certainty. As Duclaux has aptly put it, the reason why Science 

 advances is that it is never sure of anything. Thus I justify my effort of to-day. 



Notwithstanding this inadequate treatment of the subject of surface tension 

 in relation to celhdar processes, I hope I have made it in some measure clear that 

 the same force which shapes the raindrop or the molten mass of a planet is an 

 all-important factor in the causation of vital phenomena. Some of the latter 

 may not thereby be explained. We do not as yet know all that is concerned in 

 the physical state of solutions. The fact, ascertained by Rona and Michaelis, 

 that certain sugars, which neither lower nor appreciably raise surface tension 

 in their solutions, condense or are adsorbed on the surface of a solution system, 

 16 an indication that there are at least some problems with a bearing on vital 

 phenomena yet to solve. Nevertheless, what we have gained from our knowledge 

 of the laws of surface tension constitutes a distinct step in advance, and a more 

 extended application of the Gibbs-Thomson principle may throw light on the 

 causation of other vital phenomena. To that end a greatly developed science of 



