424 



NA TURE 



[August 23, 1906 



only in complexity from those exhibited in the non-living 

 world, and impelled by this reluctance he fabricates for 

 them, out of his own conceit, a special and exclusive 

 realm. The logical pressure of physical and chemical 

 conceptions forbids the postulation, by either the public 

 or the neo-vitalist, of such an incongruous entity as a 

 vital chemical element capable of blending with the familiar 

 chemical elements recognised in the material world ; yet 

 the physiological processes of life are in popular estim- 

 ation still held to be due to peculiar forces blending with 

 those of the material world, but so essentially different 

 that they can only be described as " vital." The neo- 

 vitalistic school of men of science, without adopting this 

 popular view in its entirety, retains the same term for 

 such physiological characteristics of cell processes as, with 

 our present limited knowledge and with our present in- 

 adequate methods of investigation, seem to be in disagree- 

 ment with present chemical and physical conceptions. 

 This disagreement is accentuated by the assumption of 

 directive vital forces, and since these cannot be ranged 

 alongside those of chemistry and physics, transcendental 

 phenomena may be always expectcti to occur the orderly 

 array of which as part of natural science is not merely 

 a futile but on a priori grounds an absolutely impossible 

 task. In order to justify this description as representing 

 the views of some neo-vitalists, I will quote a few sentences 

 from the presidential address delivered in 1898 by Prof. 

 Japp in the Chemical Section of this Association. This 

 address dealt with the formation of the optically active 

 substances found in vegetable and animal tissues or their 

 extracts. It asserts that " the absolute origin of com- 

 pounds of one-sided symmetry to be found in the living 

 world is a mystery as profound as the origin of life itself." 

 In regard to this it may be remarked that the absolute 

 origin of anything, living or non-living, is a mystery 

 which science does not attempt to solve, relative not 

 absolute causation being the object of scientific grouping, 

 hence this assertion does not necessarily imply any funda- 

 mental distinction between the two classes of phenomena. 

 But there is more than appears upon the surface, for the 

 whole argument leads up to the sweeping statement that 

 "no fortuitous concourse of atoms, even with all eternity 

 for them to clash and combine in, could compass this 

 feat of the formation of the first optically active organic 

 compound." It is thus inferred that because the manner 

 of such formation cannot be accounted for in the present 

 condition of scientific knowledge, its scientific causation is 

 from the nature of things unknowable. However, although 

 unknowable in the strictly scientific sense, the intellectual 

 craving for causative explanation of some sort urges Prof. 

 Japp to say, " I see no escape from the conclusion that 

 at the moment when life arose a directive force came into 

 play." There is here introduced a grandiose term for life 

 which is viewed as involving directive forces; the term, 

 however, adds nothing to our physiological knowledge, is 

 not in itself explanatory, and not only offers no new 

 method of physiological investigation, but brands as use- 

 less all the methods derived from phvsics and chemistry, 

 past, present, and future. In a recent work Prof. Moore 

 has attempted to set forth a conception which shall be 

 vitalistic in essence, and yet not so completely out of touch 

 with the principles of natural science." He regards living 

 cells as transformers of energy and .thus leaves them abso- 

 lutely dependent upon its receipt ; the transformed mode 

 which is achieved by the cells is, however, one which 

 cannot be interpreted in terms of the familiar modes pre- 

 sented in the non-living world. He terms the transformed 

 mode " biotic energy," and the distinction between this 

 and " vital directive force " appears to be its absolute 

 dependence upon the other modes for its appearance. It 

 thus does not run counter to the law of the conservation 

 of energy, and warrants, in the opinion of some, the con- 

 fident expectation that it will be found capable of precise 

 scientific expression. I confess that I am unable to share 

 this confidence. The introduction of the conception entails 

 the same double terminology to which I have referred, 

 and I feel convinced that the assumption, in the case of 

 any given physiological phenomena, of biotic energy as a 



' See article by B. Moore In "Recent Advances !n Physiology and Bio- 

 chemistry." Edited by L. Hill, F.R.S^ (London : Arnold, 1506.) 



NO. 192 1, VOL 74] 



causative explanation, would be immediately abandoned if 

 the phenomena were subsequently found to be explicable 

 on physical and chemical conceptions. Biotic energy 

 appears to me as only an intellectual compromise, an 

 abortive attempt to clothe the naked form of vitalism in 

 a decent scientific dress ; but, although partially clothed, 

 it offers, like neo-vitalism, no new method for physio- 

 logical investigation, and must, in consequence, remain 

 barren, never contributing towards physiological achieve- 

 ment. To what extent its adoption may be an intellectual 

 solace is a question which does not fall within the scope 

 of physiology. Certain physiological phenomena are 

 especially brought forward as necessitating the assumption 

 of vitalistic or biotic conceptions ; among these are the 

 phenomena of nervous activities, the formation and activi- 

 ties of enzymes, and the passige of substances through 

 living membranes. The question of the nervous activities 

 will be dealt with later ; but as regards the diffusion of 

 gases or substances in solution through cellular membranes 

 a few general considerations may be advanced now.' The 

 passage of substances into and through non-living mem- 

 branes is modified in regard to both the velocity and the 

 selective character of the passage by a large number of 

 factors, among which are nature of substance, pressure, 

 osmotic index, temperature, and the structural, electro- 

 lytic, and chemical characters of the membrane. Tissue 

 membranes, whether animal or vegetable, possess a com- 

 plicated particulate structure, and it is obvious that experi- 

 ments must be carried out extensively on dead tissue mem- 

 branes in order to determine how far the general particulate 

 arrangement may modify the rate and character of the 

 passage. In this respect our present infonnation is not 

 sufficiently extensive to warrant any definite general state- 

 ment, and such experimental evidence as exists opens up 

 difficult problems in molecular physics which still await 

 solution ; moreover, the presence of electrolytes, by assist- 

 ing adsorption, appears to modify the apparent rate and 

 character of the total passage, and further experiments are 

 necessary on this point. But in the living membrane, 

 especially when it is composed of cellular units, the whole 

 question is additionally complicated by the great prob- 

 ability that the cells are the seat of chemical processes 

 the nature of which is imperfectly known ; such processes 

 constitute the metabolism of the cells. It would, therefore, 

 be somewhat surprising if the phenomena of the passage 

 of substances through such cellular membranes were in 

 strict accord with the passage of similar substances through 

 non-living membranes which have not the same particulate 

 framework and are not the possible seat of similar chemical 

 processes. The statement, therefore, that any discrepancy 

 between the two classes of phenomena necessitates the 

 assumption of a peculiar vital directive force disregards 

 the circumstance that between the conditions in the one 

 case and those in the other lies a large and little explored 

 field ; moreover, such a statement implies, without any 

 warrant, that any physico-chemical explanation must 

 necessarily be insufficient in the case of the living mem- 

 brane, although it is realised that there mav be active 

 chemical processes of the operations of which we have at 

 present little exact knowledge. 



What possible justification is there, therefore, for brand- 

 ing as hopeless all further physical and chemical investi- 

 gation of certain aspects of the phenomena by attributing 

 these to vital directive forces? The gaps and imperfections 

 of the pal.tontological record were triumphantly vaunted 

 by the opponents of evolution ; and now that the work of 

 successive years has convincingly contributed towards the 

 filling up of these gaps not only has this objection col- 

 lapsed, but the hypothesis of special creations which it 

 supported has been involved in its fall. There are indica- 

 tions that the discrepancies in diffusion phenomena through 

 widely different structures may be knit by the results of 

 experiment on intermediate modifications. It may be many 



1 The conception of Ostwald as to the action of catalytic .substances is 

 extremely sugeestive in connection with the activities of enzymes, both in- 

 tracellular and extracellular. It is possible that the changes brought about 

 by enzymes may. with the growth of our knowledge in physical chemistry, 

 be shown to b ■ of the same order as those which sl^wlv occur in the absence 

 of enzymes, and that the enzyme itself by facilitatingadsorption phenomena 

 may merely act by accelerating the veloci'v of the special change. See 

 Leathes, " Problems in Animal Metabolism " (London ; Murray, 1906). 



