MUSCULAR SYSTEM. 295 



they form. They are very minute. Each living and growing cell 

 is made up of a cell wall containing a mass of protoplasm with its 

 nucleus, cell sap, and other cell contents. Protoplasm resembles 

 the white of an egg, but may be jellylike in consistency. Living 

 cells grow and multiply in large numbers together. Those of one 

 kind or structure are united to form a certain kind of tissue. 



There are six kinds of tissues recognized in the body: (1) 

 Muscular tissue; (2) epithelial tissue, or skin; (3) nervous tissue; 

 (4) connective tissue, which surrounds other tissues and organs, 

 holding them in place; (5) bony tissue; (6) fatty tissue. 



In order to accomplish a definite purpose and to work to the 

 best advantage, several kinds of tissues are usually associated 

 together to form organs. For example, the heart is a group of 

 different tissues working for a definite purpose. Each organ has 

 a work to perform, which is closely associated with other organs 

 working in cooperation with it. Such a combination is called a 

 system. The following systems make up the working . parts of 

 the fowl's body: Muscular, digestive, circulatory, respiratory, 

 reproductive, and nervous systems. The nervous system, and 

 others of minor importance to the poultryman, will not be dis- 

 cussed here. 



Muscular System. The muscular system has a double func- 

 tion-to perform in the case of the fowl: (1) To furnish the means 

 by which the bird can move, (2) to cover the bones and fill out 

 the body contour. This latter function tends to give the show 

 bird the highest degree of type and perfection of bodily propor- 

 tions and the standard shape. 



The character and extent to which the muscular tissue has 

 been developed determine in a large measure the value of the bird 

 for table purposes. The character and form of muscles in any 

 breed are largely inherited, but they can be influenced by feeding 

 and management. For example, the effect of close confinement 

 compared with liberal exercise on the structure of the muscular 

 tissue is easily shown. The former will produce soft flesh, fine in 

 texture, and relatively free from connective tissue; the latter will 

 produce less flesh, coarse in structure, with an increased amount 

 of connective tissue. 



Muscles vary greatly in size and thickness in different parts of 

 the body. Those of most importance, from a commercial stand- 

 point, are found chiefly on the breast and limbs. The former are 

 the muscles which control flight. 



