Fig. 79. Left Arm, Outer and Posterior Aspect. 



Skin and Fascia have been completely removed ; a large piece of the Ottter Head 

 of the Triceps, and the posterior portion of the Deltoid Muscle beloiv its origin 

 have been cut away. The Long Head of the Triceps has been drawn down- 

 wards and backwards. The Venae Comites have been removed. 



Below the Shoulder-Joint, from the anterior aspect backwards, amund the 

 Surgical Neck of the Humerus, between the Teres Minor and Teres Major, the 

 Posterior Circumflex Vessels pass (the Artery being a branch of the Axillary and 

 having 2 Venae Comites). The Circumflex Nerve accompanies them ; it supplies 

 the Deltoid and Teres Minor Muscles (cf. Fig. 77). 



Behind the outer border of the Humerus emerge tlie Musculo-Spiral Nerve 

 and the Superior Profunda Artery, as they wind around the bone in the Musculo- 

 Spiral Groove (cf. Fig. 80). The Nerve pierces the External Intermuscular Septum 

 and runs downwards to the forearm, between the Brachialis Anticus and the 

 Brachio-Radialis Muscles (cf. Fig. 81). This spiral course of the nerve is a serious 

 obstacle in extensive operations on the arm (e. g. extensive scraping of the Humerus 

 for Osteomyelitis). The Anterior and Internal surfaces are not favourable for 

 operations, owing to the large vessels; on the Posterior surface the Musculo-Spiral 

 Nerve is in the way, because its course is not a straight one, like that of the 

 nerves in the thigh. Its close proximity to the bone explains why it is so often 

 injured in fractures, and why it may be pressed upon by or be embedded in 

 Callus-formation. 



The Ulnar Nerve runs for a short distance parallel to the Long Head of 

 the Triceps. 



The Superior Profunda Artery anastomosing, by means of a Recurrent 

 Branch, with the Posterior Circumflex Artery, supplies the Triceps and the Humerus 

 (nutrient artery) and divides into an Anterior and a Posterior Division. The former 

 accompanies the Musculo-Spiral Nerve and ends by anastomosing with the Radial 

 Recurrent Artery. The latter runs in the substance of the Inner Head of the 

 Triceps downwards to the Olecranon where it anastomoses with the Interosseous 

 Recurrent Artery. 



