28 



clavian artery. But this position of the parts is quite unnatural, 

 and is only brought about by disturbing the relations of the struc- 

 tures during dissection. In the illustrations depicting the brachial 

 plexus in text books the results of this unnatural traction are easily 

 seen. In the illustration in Poikrier's "Traitö d'Anatoraie humaine" to 

 which reference has already been made, the artery is, however, clearly 

 shown lying in the position which I have described, but unfortunately 

 the nerve trunk is not continued in the drawing so as to occupy the 

 empty groove. 



It is therefore quite inaccurate to describe any impression on the 

 first rib as "the groove for the subclavian artery" or as the "sulcus 

 subclaviae" (B.N, A.), because the furrow thus described is certainly 

 caused by (and in the undisturbed body is occupied by) the inferior 

 trunk of the brachial plexus. It is in fact the "sulcus nervi brachialis". 

 (See Figs. 1 and 2.) 



The relations of the first rib, as a whole, are not well described, 

 or figured, in most text books of Anatomy; and one muscular im- 

 pression — that of the scalenus medius — is usually depicted incor- 

 rectly on the dry bone, while it is correctly shown in illustrations 

 of the muscle in the same books. Poirriee, in his "Trait6 d'Anatomie 

 humaine" (Tome 2, Fasc. 1, p. 401) correctly describes in this in- 

 sertion — "ä la face sup6rieure (externe) et au bord externe de la 

 premiere cote". Yet the common site of its insertion, as marked upon 

 the bone, is upon the inner border of the first rib. 



Since fibres of the scalenus medius not infrequently pass to the 

 second rib, it is obvious that such a limitation of its insertion to the 

 inner border of the first rib is incorrect. 



The rough area of the insertion of the scalenus medius is well 

 marked on most bones, and it extends from the posterior edge of the 

 so-called "sulcus subclaviae" backwards towards the tuberosity, to the 

 point where the deep portion of the scalenus posticus gains attach- 

 ment. This impression runs to the outer margin of the rib for practi- 

 cally the whole of its extent, leaving only a small portion of the 

 convex outer border of the rib bare anteriorly. The first digitation 

 of the serratus magnus takes origin from the outer border of the 

 first rib immediately posterior to the "sulcus subclaviae", to the outer 

 side of the insertion of the scalenus medius. 



To the inner border of the first rib is attached the fascia 

 (Sibson's fascia) which represents the degenerated scalenus minimus 

 of Albinus. 



