1 6 ANATOMY AND PHYSIOLOGY FOR NURSES 



normal proportion of earthy matter, whereas the animal 

 matter is of unhealthy quality. 



Cartilage is a non-vascular structure which is found 

 in various parts of the body in adult life chiefly in the 

 joints, in the parietes of the thorax, and in various tubes, 

 such as air-passages, nostrils, and ears, which are to be 

 kept permanently open. In the fetus, at an early period, 

 the greater part of the skeleton is cartilaginous. As this 

 fetal cartilage is afterward replaced by bones, it is called 

 "temporary," in contradistinction to that which remains 

 unossified during the whole of life, and which is called 

 "permanent." The first forms the original framework 

 of the skeleton, and becomes ossified. Permanent car- 

 tilage is not prone to ossification. 



Cartilages are classified, according to their function and 

 position, into articular, interarticular, costal, and mem- 

 braniform. Cartilage is divided, as to its minute struc- 

 ture, into true or hyaline cartilage, fibrous or fibrocarti- 

 lage, and yellow, elastic, or reticular cartilage. 



Articular cartilage forms a thin layer upon the 

 joint-surfaces of the bones, and its elasticity enables it 

 to break the force of any concussion, while the smoothness 

 affords ease and freedom of movement. It varies in 

 thickness according to the shape of the bone on which it 

 lies. A cartilage derives its nutriment partly from the 

 vessels of the neighboring synovial membrane as well as 

 from the bones upon which they are implanted. 



Marrow. The marrow is a complex tissue which 

 fills up the cylindric cavity in the shafts of the long bones; 

 it also occupies the spaces of the cancellous tissue and ex- 

 tends into the larger bony canals (Haversian canals) 

 which contain the blood-vessels. It is of two colors, 

 yellow and red; the former is found in the long bones of 

 the adult, and is composed of fat 96 per cent., areolar 

 tissue and vessels i per cent., fluid 3 per cent., with ex- 



