ADDENDUM. 



Pronator Quadratus. 



Origin. From the antero-internal surface of the ulna 

 for its lower one-fourth. 



Insertion. Into the anterior surface and outer border of 

 the radius for its lower one-fourth. 



Nerve Supply. The anterior interosseous (median). 



Action. To pronate the forearm. 



The Axillary Space. This is an irregularly-shaped pyra- 

 mid, with the following boundaries : 



Anteriorly, the clavicle ; the subclavius, pectoralis major 

 and minor muscles ; the costocoracoid membrane ; the pec- 

 toral and clavipectoral fasciae (the latter an extension of 

 the costocoracoid membrane). 



Posteriorly, the subscapularis, teres major, and latissimus 

 dorsi muscles. 



Internally, the serratus magnus muscle ; portions of the 

 first to the fourth ribs inclusive, with the intervening mus- 

 cles and fascia. 



Externally, the upper portion of the humerus ; long 

 head of the biceps and the coracobrachialis. 



The apex is between the clavicle and first rib, and is 

 occupied by the brachial plexus and large blood vessels. 



The base is formed by the axillary fascia. 



The average weight of the adult human brain is, for 

 males, 49^ ounces ; for females, 44 ounces. 



648 



