Life as a Physical Phenomenon. 161 



The principal features which distinguish what are 

 called organic from inorganic bodies are thus given by 

 one of the latest as well as one of the best and most com- 

 plete works on physiology : ' 



1st. Minerals grow by accretion, plants and animals by 

 living processes. 



2d. The form of organic bodies is determinate ; but a 

 determinate form is not essential to minerals. 



3d. In size organic bodies are determinate, while mine- 

 rals deviate from any given standard of bulk. 



4th. They differ in chemical composition. 



5th. They differ in structure. 



6th. Minerals are more permanent than organic structures. 



7th. Organic bodies are all derived from parents. 



Here, then, we have the full array of causes for vitality, 

 and our author comments at length upon each of these 

 distinguishing characteristics. 



But will they stand the test of a rigid examination, 

 so far as establishing the necessity of a new force is 

 concerned? 



" Minerals " are said " to grow by accretion, plants and 

 animals by living processes." 



Let us examine a living structure, and see whether it 

 has any comment upon this proposition. 



There exist in more or less abundance in most plants, 

 crystals which often occupy the centre of a cell. In the 

 tissues at the base of an onion may be found myriads of 

 the most beautiful crystals. Here we have a compound 

 crystal, in the form of a Greek cross, perfect in its sym- 

 metrical beauty, with its angles and planes more exact than 

 could have been formed by the most skillful human mecha- 

 nism, composed of four prisms grouped in such geometri- 



1 Marshall. 



'[Trans. vi.~\ 21 



