STRUCTURAL CHARACTERS OF ANIMAL ORGANISMS. 61 



by many blood vessels, and the fibres are in immediate relation to 

 certain nerves which terminate in them. The various secreting 

 organs are made up of epithelial cells, held together by connective 

 tissue and in close relation to blood vessels and nerves, and are so 

 arranged that they pour their secretion into a duct. The bones, 

 which are the organs which give the body support, contain, in 

 addition to the bone tissue of which they are composed, a great 

 quantity of indifferent cells, fat cells, nerves, and blood vessels. 

 They are covered on the outside with a tough vascular coat, which 

 gives them strength, assists their nutritive repair and reproduc- 

 tion, and acts as a point of attachment for the muscles and liga- 

 ments. Where the bones are in immediate relation at the joints, 

 they are commonly tipped with cartilage. 



If, then, we analyze anatomically the architecture of the 

 human body, we shall find that it is made up of a number of 

 complex parts, each adapted to some special function, and com- 

 posed of such an association of the simple tissues as the special 

 part demands. 



The general arrangement of these organs and their modes of 

 action will be discussed in a future chapter. 



