78 ANATOMY AND PHYSIOLOGY 



animal matter like cartilage, appears about the fracture, forming 

 a callus. This is soon hardened by deposit of mineral matter and 

 the callus becomes bone, but the mark of fracture and repair will 

 always remain. The callus will form and unite the ends of bone 

 even if they are not well matched, but in this case deformity will 

 result. If the callus does not harden the union is fibrous. 



Surgical note. " Setting" a fractured bone consists in placing 

 the ends in proper position, or "apposition." This, nature can- 

 not do, because the muscles above and below are pulling them 

 out of place, therefore the skill of the surgeon is required for its 

 accomplishment. 



Practical point. The nursing care of a fracture is directed to 

 the end of keeping the bone supported in position, and as far as 

 may be, perfectly quiet until the callus is hardened, so that the 

 least possible deformity will remain. To accomplish this the 

 nurse must not only have a knowledge of anatomy, but must 

 exercise skill and judgment to an unusual degree. 



PHYSIOLOGY OF BONE AND THE SKELETON 



At first thought it would appear that not much could be said 

 concerning the physiology of bone tissue, which is a finished prod- 

 uct, the changes which it undergoes being directed solely to its 

 own preservation. The ability of bone to repair injuries by utiliz- 

 ing material from the blood is, however, a physiologic process; 

 and the membranes which cover bony surfaces (periosteum 

 outside, endosteum within medullary canals) have a well-defined 

 function in the formation of bone tissues, already referred to. 

 One of the most important functions of the body, namely: pro- 

 viding an origin for cells (or corpuscles) of the blood, belongs to the 

 marrow of bones. Cancellous bone contains in its spaces thin red 

 marrow (the "red bone marrow" of clinic use) in which red cells 

 have their origin, while the medullary canals of long bones contain 

 a firmer fatty marrow where many of the white cells of the blood 

 have their beginning. 



Taking a broad view, we find many points of interest in the 

 bones and the skeleton which they comprise, some of which have 

 already been touched upon. It is their mechanical physiology 

 which is conspicuous and of great importance they afford attach- 

 ment to muscles; they enclose cavities; they sustain pressure. 



