MANUAL OF ZOOLOGY. 



2. DIFFERENCES BETWEEN DEAD AND LIVING BODIES. 



In determining this somewhat difficult point, it will be best 

 to examine the differences between organised and unorganised 

 bodies seriatim, and to compare them together systematically 

 under the following heads : 



a. Chemical Composition. Unorganised bodies are composed 

 of many elements, which may be either simple or combined ; 

 but the combinations are mostly limited to a small number of 

 elements (forming binary and ternary compounds), and these 

 are united in low combining proportions. Thus, carbonate of 

 lime, or common limestone, is an excellent example of an in- 

 organic body,* being a ternary compound composed of one 

 atom of the metal calcium, three of oxygen, and one of carbon. 



Organised bodies, on the other hand, as well as those which, 

 though dead, have been directly produced by the living 

 organism, are composed of few chemical elements, and these 

 are almost always combined. Furthermore, the combinations 

 are always complex (ternary and quaternary compounds), and 

 the elements enter into union in high combining proportions. 

 Finally, the combinations are invariably characterised by the 

 presence of water, and are prone to spontaneous decomposition. 

 Thus, the great organic compound, albumen, is composed of 

 144 atoms of carbon, no of hydrogen, 18 of nitrogen, 2 atoms 

 of sulphur, and 42 of oxygen. Iron, however, exists in the 

 blood, very probably in its elemental condition ; and copper 

 has been detected in the liver of certain Mammalia, and 

 largely in the red colouring-matter of the feathers of certain 

 birds. 



b. Arrangement of Parts. Unorganised bodies are composed 

 of an aggregation of homogeneous parts (when unmixed) which 

 bear no definite and fixed relations to one another. 



Organised bodies are composed of heterogeneous parts, the 

 relations of which amongst themselves are more or less definite. 



c. Form. Unorganised bodies are either of no definite shape 

 when they are said to be "amorphous" or they are crys- 

 talline, in which case they are almost invariably bounded by 



certain living beings (Foraminiferd) cannot be said to be "organised" in 

 the proper sense of the term ; still organisation is in such a vast proportion 

 of cases the concomitant of vitality, that the purpose here in view will be 

 fully served by assuming that all living bodies are organised, and all dead 

 bodies are unorganised. 



* In another sense limestone may be said to be organic namely, when it 

 has been produced by the operations of living Beings ; but this does not 

 affect the above definition. 



