44 



ANATOMY AND PHYSIOLOGY OF 



Q, How many bones compose one of 

 the fore extremities ? — A. Twenty-one. 



OF THE SHOULDER. 



Q. The shoulder being composed of the 

 scapula and hnnienis, what portion of the 

 thorax do they occupy ? — A. They occupy 

 its antero-lateral region. 



SCAPULA, (shoulder BLADe). 



Q. What is the position of the scap- 

 ula ? — A. It occupies the antero-lateral 

 parts of the thorax. 



Q. Describe the bone. — A. It is trian- 

 gular, broad, and thin superiorly ; narrower 

 and thicker inferiorly; its external surface 

 is unequally divided into two superficial 

 concavities, named fossas antea et postea 

 spinatsE. Its internal sm-face is smooth, yet 

 excavated. 



Q. Describe the borders. — A. The su- 

 perior has a thin, roughened summit for 

 the insertion of the cartilage of the scap- 

 ula ; the anterior is thin in its upper half, 

 yet below it becomes romided ; the posterior 

 is obtuse and rounded. 



Q. How does the scapula terminate in- 

 feriorly ? — A. By a glenoid cavity. 



Q. What are the connections of the 

 scapula ? — A. It has a ligamentous con- 

 nection with the spines of some of the dorsal 

 vertebrae ; to the thorax, it is connected by 

 muscular faschia; and its inferior connec- 

 tion is by means of the glenoid cavity, to 

 the head of the humerus ; this latter forms 

 the shoulder joint. 



-Q. Is there anything remarkable about 

 the shoulder joint? — A. Its most remark- 

 able feature is, the great disproportion in 

 size between the head of the humerus and 

 the glenoid cavity. 



Q. How is this disproportion in magni- 

 tude compensated for ? — A. By an exten- 

 sive capsular membrane, wliich admits of 

 extensive motion. 



Q. What are the insertions of this cap- 

 sular membrane? — A. It has a circular 

 insertion into the rough margin of the 

 glenoid cavity, and also around the neck of 

 the humerus. 



Q. How is this membrane protected in- 

 ternally and externally ? — A. Internally it 

 is clothed with a synovial membrane ; ex- 

 ternally by adherent muscles. 



HUMERUS. 



Q. What is the situation of the 

 humerus ? — A. It is situated beneath the 

 scapula, occupying a diverse direction, viz., 

 downwards and backwards, and is in con- 

 tiguity with the lateral parts of the thorax. 



Q. Describe the form of the humerus. 

 — A. It is irregular, cylindroid, having a 

 convoluted appearance, and its superior 

 extremity is much larger than the inferior. 



Q. How is this bone divided? — A. 

 Into a body, superior and inferior extremi- 

 ties. 



Q. Describe the bod?/. — A. It is angu- 

 lar, with sides, contracted superiorly, and 

 flattened and rounded inferiorly. From its 

 superior-anterior-lateral margin projects a 

 roughened tuberosity, into which the leva- 

 tor humeri is inserted. The lateral part of 

 the body is hollow or excavated. The in- 

 ner side is somewhat roughened and promi- 

 nent. 



Q. Describe the superior extremity. — 

 A. The superior extremity being much 

 larger than the inferior, presents a head 

 and several tubercles : it has a projecting, 

 hemispherical surface, designed for exten- 

 sive articulation. It presents a smooth 

 surface, yet has an irregular, indented 

 groove for the insertion of a capsular liga- 

 ment. 



Q. What is the use of the tubercles ? — 

 A. The anterior, three in number, serve as 

 articulations for the flexor brachii to tra- 

 verse. The fourth serves as a protection 

 against dislocation. 



Q. Describe the inferior extremity. — A. 

 It consists of two heads or condyles, sepa- 

 rated by deep ovoid fossa, into which is 

 received the olecranon of the ulna. 



Q. What are the connections of the 

 humerus ? — A. Superiorly, it connects 

 with the scapula ; inferiorly, it articulates 

 with the radial and ulnar extremity of the 

 Os Brachii. 



