ANATOMY IN A NUTSHELL. 19 



All processes of bone are either apophyses or epiphyses. An apophysis is 

 a process that has grown from the bone and has no separate ossific center. An 

 epiphysis has a separate ossific center and is joined to another bone by car- 

 tilage. This cartilage becomes ossified but this change does not make the 

 epiphysis an apophysis. Once an epiphysis always an epiphysis. The head 

 of the femur is an epiphysis ami the neck of the femur is an apophysis. 



The nutrient arteries of the bones of the arm and forearm run towards 

 the elbow: in bones of the lower extremity they run from the knee. 



Rule 1. — The epiphysis towards which the nutrient artery runs joins the 

 bone first always, but ossifies last in all bones except the fibula. 



Rule 2. — When there is but one epiphysis then the nutrient artery runs 

 towards the end of the bone which has no epiphysis; e. g., the clavicle and met- 

 acarpals and metatarsals. (Plate VII.) 



Rule 3. — When there are two or more nucleii in an epiphysis they con- 

 solidate before the epiphysis joins the diaphysis. 



Rule 4. — The epiphysis which ossifies first is the larger, and the cartilage 

 between it and the diaphysis grows longer and faster than the cartilage at the 

 other extremity of the bone. 



An epiphysis may become separated from the diaphysis and such an in- 

 jury may be mistaken for a fracture or dislocation. A knowledge of this prin- 

 ciple is of great importance in medical jurisprudence; e. g.. the epiphysis at the 

 distal end of the femur ossifies at the ninth month of fetal life. 



The covering of bone is called periosteum. It covers all the bone except 

 the articular cartilage and uives attachment to tendons. Periosteum besides 

 giving attachment to the tendons of muscles; 



1. Gives nutrition to the bone. 



2. Forms all capsular ligaments. 



.'!. Tends to hold the end of broken bones. 



4. From it the bone grows in thickness. 



5. It hinders the progress of contiguous inflammation. 



A long bone grows in length by the development of the epiphyseal cartil- 

 age and interstitial deposits; in thickness from the osteogenetic layer of the 

 periosteum and interstitial deposits. 



There are 300 bones in the body (Platel.) They are divided into long, 

 short . flat and irregular ones. 90 of the bones are Long ones and are found 

 in the extremities. In reality a long bone may not be :is long as a Hat or irreg- 

 ular one o]- even a short bone. e. g., the last phlanx is shorter than the os calcis. 

 The long bones act as lexers and have a medullary canal in the center of each ; 

 and a shaft called diaphysis. and two extremities. They are developed by 

 osseous deposits in cartilage. In each upper extremity there is a clavicle, 

 humerus, ulna, radius, five metacarpal and fourteen phalanges, making 23 long 

 bones in each upper extremity, then in both extremities there are 2x23 or 16 

 long bono. In each lower extremity there is a femur, tibia, fibula, five met- 

 atarsals ami fourteen phalanges, making 22 long bones in each lower extremity, 

 then in both extremities there are 2x22, or II long bono. The 46 long bone- 

 in the upper extremity and the 44 long ones in the lower extremities make 



