46 NUTRITION OF FARM AMIMALS 



to form organs, such as the muscles, heart, lungs, stomach, 

 liver and the like, each performing its special part in the com- 

 plex interplay of activities necessary for the life of the organism 

 as a whole. 



Since this is not a treatise on anatomy, it is unnecessary to 

 consider in detail all the diverse types of tissue or all the various 

 organs making up the body. It is desirable, however, that the 

 student of nutrition should acquire some notion of the chemical 

 make-up of the various parts of the body. For this purpose it 

 will be convenient to use the following scheme, based chiefly 

 on the functions performed by the different groups of tissues, 

 which ignores to some extent the distinction between tissues 

 and organs and which does not pretend to be an exact or ex- 

 haustive classification. 



First : The supporting tissues, including bone, tendon, carti- 

 lage, ligament, elastic tissue, etc. 



Second : The tissues of motion, including the muscular 

 tissues and the nerve tissues or the nervous system. 



Third : The tissues of alimentation, including the tissues 

 and organs concerned in digestion, resorption, circulation, 

 respiration and excretion. 



Fourth : The epidermal' tissues. 



Fifth : The reserve tissues, including, besides adipose 

 tissue, those tissues in which glycogen is more or less abun- 

 dantly stored. 



The supporting tissues 



79. Intercellular substance. In the bodies of the higher 

 animals certain tissues show an enormous development of the 

 so-called intercellular substance, so that the cells, instead of 

 closely adjoining each other, are imbedded in a mass of non- 

 cellular material which may vary greatly in consistency. Some- 

 times this intercellular substance is entirely homogeneous but 

 it usually contains a greater or less number of fibers imbedded in 

 a homogeneous basis. By virtue of the special properties of 

 the intercellular substance, tissues of this sort perform pri- 

 marily mechanical functions, maintaining the form of the body 

 or serving to connect and support other tissues, while the cells 

 themselves serve principally to produce and maintain the inter- 

 cellular substance. The organic basis of the latter is the group 



