198 
J. Bret land Farmer. 
we can now confidently predict colour, explosiveness, and many 
other properties, from a knowledge of their chemical constitution, 
so we shall be able to explain the phenomena of symmetry, variations,, 
and other form-relations, in very much simpler terms than are 
possible to-day. 
I believe it is legitimate to draw a distinction between two sets 
of factors concerned in the production and maintenance of a living 
organism, the one is material, the other dynamical—put in this 
form probably no one would object, and left in this form I do not 
suppose the matter would be much advanced. But I think one may 
go even further, and regard the material basis as analogous to a 
mechanism, tuned to respond to certain stimuli in certain ways, the 
final character of each individual or each organ being the result of 
particular stimuli acting on particular kinds of mechanism. 
Chemical substances are precisely the same. A stimulus which will 
provoke one kind of response when acting on one material 
mechanism will provoke one of a different kind if it can affect a 
differently built machine. In endeavouring to translate these 
metaphors into something more directly similar to the things them¬ 
selves, one is impressed with the fact that in the material substratum 
of a plant or of an animal we have to deal with vastly complex 
bodies, diverse in different organisms, capable of constantly under¬ 
going change, as evidenced by growth and decay, disintegration and 
separation. These functions of metabolism are universally charac¬ 
teristic of living things and are associated with the protoplasmic 
body. And therein some unity of ground-plan seems to be indi¬ 
cated, and the clue is probably to be sought in the architectural 
conformation, that is in the chemical mechanism of the protoplasm 
itself, whether the units be termed biogens, micellae, or molecules. 
At any rate there is good reason for supposing the structure is 
highly complex, and that in some way a system that includes 
nitrogen within its boundaries is more or less loosely associated 
with one of carbohydrate-like structure. But the point is, that so long, 
as the manifestation of vitality remains possible, the mechanism or 
arrangement is capable of being set in molecular motion and of 
undergoing certain more or less well-defined serial transformations 
when acted upon by appropriate stimuli. These changes may mani¬ 
fest themselves as physical, chemical or electrical disturbances, or 
in some combination of these. And although we are as yet unable 
to form any probably accurate guess as to the precise nature or 
character of the mechanism, nevertheless we can hardly escape the 
