chap, xii.] THE ARM, 205 



insertion to the outer condyle on the one side, and 

 from the coraco-hrachialis insertion to the inner condyle 

 on the other. By means of this aponeurosis and its 

 septa the arm is divided into two compartments, that 

 can be well seen in transverse sections of the limb. 

 These compartments serve to confine inflammatory 

 and hsemorrhagic effusions. The anterior of the two 

 spaces has the less substantial boundaries, owing to 

 the thinness of the brachial fascia as it covers the 

 biceps. Effusions can readily pass from one compart- 

 ment to the other by following the course of those 

 structures that, by piercing the intermuscular septa, 

 are common to both spaces. These are the musculo- 

 ppiral and ulnar nerves, the superior and inferior 

 profunda, and anastomotic arteries. The principal 

 structures that pierce the brachial aponeurosis itself 

 are the basilic vein, a little below the middle of the 

 arm, the internal cutaneous nerve, about the middle, 

 and the external cutaneous nerve, just above the 

 elbow. The two first named are in the inner bicipital 

 groove, and the last named in the outer. 



The skin over the point of insertion of the deltoid 

 was commonly selected as a suitable place for an issue 

 at a time when that remedy was popular. The reasons 

 for such selection were the absence of blood-vessels of 

 any size in the parts beneath, and the freedom of the 

 spot from muscular movement. The brachialis anticus 

 is closely adherent to the bone, while the biceps is 

 free. It follows, therefore, that in section of these 

 muscles, as in amputation, the latter muscle retracts 

 more considerably than does the former. It is well, 

 therefore, in performing a circular amputation, to 

 divide the biceps muscle first, and then after it has 

 retracted to cut the brachialis anticus. 



The foracliial artery. The line of this vessel 

 has already been given. It is well to note that in the 

 very muscular the artery may be overlapped to a 



