IV] AND STRUCTURE OF THE CELL 291 



or in the simplest cases it seems to sheWj is that of a more or less 

 viscous colloid, or rather mixtm:e of colloids, and nothing more. 

 Now, as Clerk Maxwell puts it in discussing this very problem, 

 "one material system can differ from another only in the configura- 

 tion and motion which it has at a given instant*." If we cannot 

 assume differences in structure or configuration, we must assume 

 differences in motion, that is to say in energy. And if we cannot 

 do this, then indeed we are thrown back upon modes of reasoning 

 unauthorised in physical science, and shall find ourselves constrained 

 to assume, or to "admit, that the properties of a germ are not those 

 of a purely material system." 



But we are by no means necessarily in this dilemma. For though 

 we come perilously near to it when we contemplate the lowest 

 orders of magnitude to which hfe has been attributed, yet in the 

 case of the ordinary cell, or ordinary egg or germ which is going 

 to develop into a complex organism, if we have no reason to assume 

 or to beheve that it comprises an intricate "mechanism," we mgiy 

 be quite sure, both on direct and indirect evidence, that, hke the 

 powder in our rocket, it is very heterogeneous in its structure. 

 It is a mixture of substances of various kinds, more or less fluid, 

 more or less mobile, influenced in various ways by chemical, electrical, 

 osmotic and other forces, and in their admixture separated by a 

 multitude of surfaces or boundaries, at which these or certain of 

 these forces are made manifest. 



Indeed, such an arrangement as this is already enough to con- 

 stitute a "mechanism"; for we must be very careful not to let our 

 physical or physiological concept of mechanism be narrowed to an 

 interpretation of the term derived from the comphcated contrivances 

 of himaan skill. From the physical point of view, we understand 

 by a "mechanism" w^hatsoever checks or controls, and guides into 

 determinate paths, the workings of energy: in other words, what- 

 soever leads in the degradation of energy to its manifestation in 

 some form of work, at a stage short of that ultimate degradation 

 which lapses in uniformly diffused heat. This, as Warburg has well 

 explained, is the general effect or function of the physiological 

 machine, and in particular of that part of it which we call "cell- 



* Precisely as in the Lueretian concursus, motus, ordo, positura, figurae, whereby 

 bodies mutato ordine mutant naturam. 



