INTRODUCTORY: THE ANIMAL ORGANISM 



19 



and eating its food which are different from those of one 

 whose diet is vegetarian. This correspondence between 

 organisation and mode of life is known as adaptation. 



Organisation involves more than the mere existence of 

 organs, more, that is, than the shaping of the 

 body into regions where special functions are 

 performed. It involves also a specialisation of each of 

 these regions to fit it for its special functions. This 



Tissues. 



...H.c. 



lac. 



Fig. 4.— A section of dry bone magnified. The dark spaces show 

 where the living part of the tissue was lodged. 



lac, Spaces known as "lacunas." In these lay the cells into which the 

 protoplasm was divided, g. s., ground-substance. This is traversed by 

 numerous "canaliculi" in which processes of protoplasm united the cells 

 into a meshwork. H.c, "Haversian canals" in which minute blood 

 vessels lay. The lacunae are so arranged as to divide the ground-sub- 

 stance into concentric layers or " lamellae " around the Haversian canals. 



specialisation is found partly in the shape of each organ, 

 but also largely in its texture and composition. The sub- 

 stance of the body is not alike throughout, but different 

 portions of it have differences in texture and chemical 

 composition which confer upon them different properties. 

 Thus the outer layer of the skin is firm and hard to pene- 

 trate, bone is rigid, blood is fluid, the substance known as 

 " connective tissue " is tough and binds other tissues 



