58 NUTRITION OF FARM ANIMALS 



The reserve tissues 



93. Food storage. The classes of tissue considered in the 

 foregoing paragraphs may be said in a general way to constitute 

 the working machinery of the body. They are composed of 

 cells which either serve the organism through specific activities 

 of their protoplasm, as by producing motion of one sort or an- 

 other, transmitting stimuli or secreting enzyms or other prod- 

 ucts, or which, by means of the extraordinary development 

 of their intercellular substance, support and protect the various 

 organs of the body as a whole. 



As previously stated, however (77), many cells have the 

 power of storing up surplus food in the form of cell enclosures, 

 especially as fat or glycogen, which apparently constitute 

 no part of the protoplasm itself but which are simply re- 

 serve material. This is more or less true of all cells, but 

 certain tissues show this property to a marked degree so that 

 they may properly be spoken of as preeminently the reserve 

 tissues. 



94. Adipose tissue. The most familiar and most im- 

 portant form of reserve tissue is adipose tissue, in which the 

 stored material consists of fat and which constitutes the great 

 store of reserve material in the animal body. 



Fat in the form of minute droplets may be deposited in the 

 cytoplasm of all body cells but the presence of more than minute 



amounts in normal cells of muscles, 

 -.-_. Nucleus, nerves, glands, etc., is unusual. 



It is particularly in certain cells 

 of the connective tissue that the 

 Fat drop. large accumulations of visible fat 



Cell-membrane. j n t h e body take place. At the 

 outset these cells present no special 

 / ^ fa V d !; characters, but in a well-nourished 



(Bohm, Davidorf, Huber, Text Book , . 



of Histology.) animal globules of fat begin to 



accumulate in them, the cells en- 

 large, the globules of fat coalesce into larger ones and finally 

 the cell substance is reduced to a mere envelope, cytoplasm 

 and nucleus being pushed to one side and almost the whole 

 volume of the cell occupied by fat. Masses of connective tissue 

 thus loaded with fat constitute adipose tissue. 



