27 



tension of which forms a trough in which the nerve lies. (This re- 

 lation is well depicted by Nicolas; — seePoiRRiER, Traits d' Anatomie 

 humaine, Tome 4, Fasc. 2, Fig. 539, p. 292.) 



Following this fascial sheath the nerve trunk reaches the inner 

 border of the rib, and enters the smooth groove known as the "sulcus 

 subclaviae". In this groove it lies in contact with the upper surface of 

 the first rib, and it is easily seen that the nerve trunk is the causal 

 factor in the production of the groove, and is its real occupant. 



The subclavian artery as it emerges from the thorax pursues an 

 altogether different course, being directed from within outwards, and 



M. Scalen, med. Tuberculum costae 



' 1 



__N.cerv.VIII 



Capitulum 

 — — ^ - N. dors. I 



M. Scalen, 

 ant. 



Art. subcl. 



Fig. 3. 



Fig. 4. 



not obliquely outwards and forwards as the nerve is. (See Figs. 3 

 and 4.) It does not lie in contact with the bone, nor strictly speaking 

 occupy the groove, but curves round the posterior margin of the scale- 

 nus anticus above the nerve trunk, and is lodged between the nerve 

 and the insertion of the scalenus anticus. (See Figs. 3 and 4.) 



The manner in which the dissection of this region is usually car- 

 ried out is probably responsible for the statement that the groove is 

 caused by, and lodges, the subclavian artery. When the arm of a 

 dead subject is forcibly raised from the side, the resisting nerves 

 are stretched and pulled upwards, and the lowest trunk of the brachial 

 plexus, when dissected out, appears to lie altogether above the sub- 



