THE CONNECTIVE TISSUES. 



13 



the fibres. In the mammals they are placed upon the periphery 

 of the fibres (Fig. 1 2, n), in the lower vertebratesynear the cen- 

 tre. The muscles of the heart agree in origin and cross-band- 

 ing with the voluntary muscles, but differ in being cellular rather 

 than syncytial, and in being removed from the control of the 

 will. All cross-banded muscles are capable of rapid contrac- 

 tions. 



The connective tissues are all of mesenchymatous origin, and 

 are characterized by a great development of the intercellular 

 substance, which 

 is usually a pro- 

 duct of the cells. 

 They are the sup- 

 porting tissues of 

 the body, and 

 vary accordingly 

 as this intercellu- 

 lar substance va- 

 ries, and may 

 correspondingly 

 be grouped under 

 several subheads, -„ ,, ir-i, i ^■ 



tlG. 13. Fibrous non-elastic connective tissue 



the principal ones (from Martin). 



being enumerated below. 



In fibrous connective tissue (white or non-elastic tissue) the 



cells are branched or spindle-shaped, and the intercellular sub- 

 stance is more or less fibrous, 

 the fibres being parallel, in- 

 terlaced, or in a network, so 

 that there result sheets, mem- 

 branes, or bundles, accord- 

 ingly as the part to be played 

 varies. In some cases this tis- 

 sue is loose (areolar tissue), 

 such as is found between the 

 skin and deeper parts ; at 

 other times it is much firmer, 



as in the case of tendons. This type of tissue also gives rise to 



Fig. 14. Fat. 0, oil globules in the 

 connective tissue cells. 



