558 ELEMENTARY PHYSIOLOGY less. 



have already described and which present every transition 

 between ordinary cartilage and ordinary connective tissue 

 (epiglottis, intervertebral ligaments). Where a tendon is 

 inserted into a cartilage, as in the case of the tendo Achillis, 

 (Fig. 90), the passage of the cartilage into the tendon is 

 beautifully displayed. The intercellular substance of the 

 cartilage gradually takes on the characters of that of the 

 tendon, and the corpuscles of the cartilage become 

 connective-tissue corpuscles. 



(e) The intercellular substance may largely disappear 

 and the interlacing bundles of collagenous fibres may 

 actually join together at the points when they cross one 

 another. In this way a spongy network of branching 

 fibres may be formed whose meshes are filled with fluid, 

 as in the lymphatic glands. 



(/) Finally, in many parts of the body fatty matter is 

 found within the protoplasmic substance of the connective 

 tissue corpuscles just as we have seen it to be formed in 

 cartilage corpuscles. 



In this way we ai'rive at modifications of the funda- 

 mental type of connective (areolar) tissue which are so 

 characteristic as to merit separate description. 



(ii.) W^hite Fibrous Tissue. This form is met with in 

 the dense and strong connective tissue of which tendons 

 and most ligaments are composed. In these structures 

 the collagenous fibres of areolar tissue are arranged in 

 dense, parallel bundles, among which are a certain number 

 of peculiarly flattened connective tissue corpuscles, 

 arranged in rows and now called tendon cells. The 

 structure of a tendon thus provides the qualities so 

 essential to it of great strength, complete flexibility, but 

 absolute want of all elasticity or extensibility. 



(iii.) Yellow Elastic Tissue. — This form occurs 

 typically in the strong ligament (liiiamentuni nuchae) at the 

 back of the neck (see Fig. 102, b) which, while giving support 

 to the head, permits it at the same time to be bent 

 forward, since the ligament is extensible. This ligament 



