THE SKELETON 3 1 



Sagittal refers to the plane bisecting the animal in a vertical 

 and longitudinal direction. Medial and lateral are adjectives, 

 the former meaning nearer to the sagittal plane and the latter 

 more remote on either side of that plane. Proximal, distad, 

 craniad, caudad, mediad and laterad are adverbs indicating direc- 

 tion in accordance with the adjectives to which they are 

 related. 



A process is projection or elevation. 



A tuberosity is a rough obtuse process. 



A tubercle is a small and usually more or less pointed process. 



A condyle is a rounded and somewhat elongated smooth 

 articular process. The distal end of the femur presents a 

 pair of condyles (Fig. 41). 



A fossa is an irregular depressed area (Fig. 31). 



A foramen is an aperture for the passage of vessels or nerves. 



The shaft is the body or middle portion of an elongate bone. 



The head is a spheroidal prominence at one end of an elon- 

 gated bone (Fig. 41). 



The epiphysis is a small process of bone ossified from a 

 separated center. In the young animal it is attached to the 

 main bone by cartilage, but in the adult becomes a part of 

 the main bone (Fig. 13). The femur has four epiphyses, one 

 for the head, one for the distal extremity, and one for each 

 trochanter process (Fig. 41). With the exception of the pha- 

 langes, metacarpals, and metatarsals, all of the long bones 

 have an epiphyses at each extremity. In the human, these 

 epiphyses do not unite with the shaft before the sixteenth 

 year. Diploe is the spongy layer of bone between the compact 

 surface layer of the flat bones (Fig. 19). 



The articulation of a bone has reference to its contact with 

 other bones by means of joints. 



STRUCTURE OF BONE 



Every bone is completely covered except on its articulating 

 surfaces with a tough membrane, the periosteum, which serves 



