20 ANATOMY FOR NURSES. [CHAP. III. 



blood-vessels. Being so meagrely supplied with blood the vital 

 processes in cartilage are very slow, and when a portion of it is 

 absorbed in disease or removed by the knife, it is regenerated 

 very slowly. A wound in cartilage is usually at first healed by 

 connective tissue proper, which may or may not become grad- 

 ually transformed into cartilage. Nearly all cartilages receive 

 their nourishment from the perichondrium which covers them, 

 and which is a moderately vascular fibrous membrane. 



Bone. Bone is a connective tissue in which the intercellular 

 or ground substance is rendered hard by being impregnated 

 with mineral salts. 



On sawing up a bone it will be seen that it is in some parts 

 dense and close in texture, appearing like ivory, whilst in others 

 it is open and spongy, and we distinguish two forms of bony 

 tissue, the dense or compact, and the spongy or cancellated. 

 On closer examination, however, it will be seen that the bony 

 matter is everywhere porous, and that the difference between 

 the two varieties of tissue arises from the fact that the compact 

 tissue has fewer spaces and more solid matter between them, 

 and that the cancellated has larger cavities and more slender 

 intervening bony partitions. In all bones the compact tissue 

 is the stronger ; it lies on the surface of the bone and forms an 

 outer shell or crust, whilst the lighter spongy tissue is con- 

 tained within. The shafts of the long bones are almost entirely 

 made up of the compact substance, except that they are hol- 

 lowed out to form a central canal the medullary canal - 

 which contains the marrow. 1 Marrow is also found in the 

 spongy portions of the bone in the spaces between the bony 

 partitions. 



The hard substance of all bone is arranged in bundles of 

 bony fibres or lamellce, which in the cancellated texture join 

 and meet together so as to form a structure resembling lattice- 

 work (cancelli), arid whence this tissue receives its name. In 

 the compact tissue these lamellae are usually arranged in rings 

 around canals which carry blood-vessels in a longitudinal direc- 

 tion through the bones. Between the lamellae are branched 



1 There are two kinds of marrow, red and yellow. Red marrow contains, 

 in 100 parts, 75 of water and 25 of solids, the solids consisting of albumin, 

 fibrin, extractive matter, salts, and a mere trace of fat. Yellow marrow con- 

 tains, in 100 parts, 96 of fat, 1 of areolar tissue and vessels, and 3 of fluid. 



