LIVING SUBSTANCE 17 



loidal, differing only in the amount of water which 

 they absorb, an amount which may be rapidly 

 altered under varying circumstances. 



Organization of Protoplasm. Not only is pro- 

 toplasm, chemically considered, a mixture of a great 

 variety of substances, but this aggregate of ma- 

 terials composing a given mass of living matter in 

 one kind of animal or plant differs from that of 

 another. Moreover, the same mass of protoplasm 

 is constantly changing with regard to the substances 

 composing it, thus making impossible anything 

 like a fixed and definite picture of its exact composi- 

 tion. But it is also true that it is not so much the 

 substances composing it, as the relations, both physi- 

 cal and chemical, that these bear to one another 

 that determines the character of the protoplasm. A 

 comparison may make this clearer. A watch is a 

 delicately constructed and complicated mechanism 

 of many parts which by their action in moving the 

 hands in certain fixed relations of time and space 

 enables us thereby to tell the time of day. It is 

 possible for any one to take such an instrument apart 

 and make a little pile of the wheels, screws, and 

 springs, but when he has done so, the mass of metal 

 and jewels that he holds in his hand is no longer a 

 watch and cannot be made to serve its original 

 purpose. The very apparent reason is that the 

 inherent quality of a watch, by virtue of which it is 

 a watch, that is, a timekeeper, is involved not only 

 in the parts composing it, but in their relations to 



