866 TRANSACTIONS OF SECTION I. 



processes, 'i'et its action was admittedly dependent on plivstcal and cliemical 

 conditions, sucli as warmth, the presence of oxygen, &c. In fact no consistent 

 definition was given to the conception of'vital force.' It consequently never 

 could become a working hypothesis of any value. Chiefly on this account, I 

 think, it practically disappeared from Physiology last century. Yet the class of 

 fact which led to the theory of ' vital force ' is now more prominent than ever ; 

 and what du llois Reymond called the ' spectre ' of Vitalism meets us at every turn, 

 thinly disguised under such names as ' cell autonomy,' ' vital processes,' &c. It 

 is useless to shut our eyes and deny the existence of this 'spectre.' We must 

 fairly face and examine it. 



However difficult it may be to imagine physico-chemical explanations of such 

 processes as respiratory exchange, secretion, muscular activity, &c., there is 

 nothing in the known facts relating to each process taken by itself to preclude 

 the possibility of such explanations. Let us then follow the Euclidian method 

 and assume provisionally tliat they are nothing but physico-chemical processes. 

 This assumption evidently implies that each of the living cells concerned has a 

 very complex and definite structure var3'ing according to its functions. To take 

 an example, a secreting cell in the kidney may be assumed to have a structure 

 which responds to the stimulus of a certain percentaEre of urea or sodium chloride 

 in the blood, and reacts in such a manner that energy derived from oxidation is 

 so directed as to perform the work of taking up urea or sodium chloride from the 

 blood and transferring it against varying osmotic pressures from one end of the 

 cell to the other. This mechanism must also be assumed to have the property of 

 maintaining itself in working order, and probably also of reproducing itself under 

 appropriate stimuli, besides also performing various other functions. Its physico- 

 chemical structure must thus be very definite and complex — to an extent which 

 the older physico-chemical theories took no account of. If we look to the cells in 

 other parts of the body we are met with the same necessity for assuming com- 

 plexities of structure which seem to grow in extent with every advance in 

 physiological knowledge, every discovery of new substances present within or 

 around the cells, every discovery of new physiological reactions. 



Let us not lose courage, however, but continue to follow the direction in 

 which our assumption leads. In assuming that the body is an enormously com- 

 plex physico-chemical structure we have only begun to face the difficulties of our 

 hypothesis: for we have still to consider how this structure can have originated 

 in accordance with the physico-chemical theory of life. The adult organism 

 develops from a single cell, the fertilised ovum. It is certain that this cell does 

 not contain in a preformed condition the structure of an adult organism. The 

 conditions of environment in which any particular ovum develops itself are 

 doubtless indefinitely complex from the physico-chemical standpoint, as indeed is 

 the environment of any particular portion of matter existing anywhere. But 

 these conditions also vary almost indefinitely in the case of different ova, whereas 

 the adult organism to which the ovum gives rise reproduces in minute detail the 

 enormously complex characters of the parent organism. AVe are thus driven to 

 the assumption that the ovum contains within itself a structure which, given 

 certain relatively simple conditions in the environment, reacts in such a way as 

 to build up step by step, from materials in the environment, the structure of the 

 adult organism. To effect this the germ-cell must have a structure almost 

 infinitely more definite and complex than that of any cell in the adult organism. 

 Difficult as it maybe to form any conception of the mechanism of a secreting cell, 

 it is infinitely more difficult to form the n^motest idea of that of a germ-cell. 



But we are still only at the beginning of the difficulty. The assumed tre- 

 mendous mechanism of the germ-cell has been developed, together with the whole 

 of the rest of the parent organism and countless other germ-cells, from a previous 

 germ-cell. What must the ' mechanism ' of this cell have been ? And that 

 of its endless predecessors ? We have reached the Euclidian reductio ad 

 absurdum. 



I might strengthen my argument by referring to the further difficulty over any 

 physico-chemical conception of what occurs in the sexual fusion of the male and 



