388 NUTRITION. 



The adipose vesicles are collected into little lobules, from 

 -% to J of an inch in diameter, 1 which are surrounded by a 

 rather wide net-work of capillary blood-vessels. Close ex- 

 amination of these vessels shows that they frequently sur- 

 round individual fat-cells, in the form of single loops. 

 There is no distribution of nerves or lymphatics to the ele- 

 ments of adipose tissue. 



It is seen by this sketch of the structure of adipose tis- 

 sue, that there is no anatomical reason for classing these 

 vesicles with the ductless glands, as is done by some physi- 

 ologists. They undoubtedly, under certain conditions, have 

 the power of filling themselves with fat ; but it would be 

 no more appropriate to call this a secretion than to apply this 

 term to the development and nutrition of the muscular sub- 

 stance within the sarcolemma. 



Conditions which influence Nutrition. We know more 

 concerning the conditions that influence the general pro- 

 cess of nutrition than about the nature of -the process itself. 

 It will be seen, for example, when we come to study the ner- 

 vous system, that there are nerves which regulate, to a 

 certain extent, the nutritive forces. We do not mean to 

 imply that nutrition is effected through the influence of the 

 nerves, but it is the fact that certain nerves, by regulating 

 the supply of blood, and perhaps by other influences, are 

 capable of modifying the nutrition of parts to a very consid- 

 erable extent. 



In discussing the influence of exercise upon the develop- 

 ment of parts, we have shown that this is not only desirable 

 but indispensable ; and the proper performance of the func- 

 tions of all parts involves the action of the nervous system. 

 It is true that the separate parts of the organism and the 

 organism as a whole have a limited existence ; but it is not 

 true that the change of nitrogenized, living substance into 

 effete matter, a process that is increased in activity by phys- 



1 LITTRE ET ROBIN, loc. cit. 



