26 



artery, and from that of the groove (here labelled "sulcus venae sub- 

 claviae") which lodges the subclavian vein. (See Fig. 1). 



The subclavian artery crosses the first rib practically at right 

 angles to the rib at the point of crossing; but the groove which is 

 supposed to be formed by it, and to lodge it, is directed obliquely 

 from behind forwards and outwards across the rib. (See Fig. 1). 



Moreover the axis of the the "sulcus subclaviae" is in line with 

 that of another and similar smooth groove upon the neck of the first 

 rib posteriorly. (See Fig. 1 "sulcus nervi cervicalis VIII".) 



Levator costae and ilio-costalis dorsi 



Scalenus 

 posterior 



Sulc. nerv. eery. VIII 



Serratus 

 magnus 



Costo-clavicular 

 ligaments and sub- — " ' 

 clavius muscle 



Fig. 1. 



Sulc. venae 

 subcl. 



Trunc. inf. plex. 

 brachialis lying in the 

 "Sulcus subclaviae" 

 B.N.A. which is thus a 

 Sulc. nervi brachialis 



Fig. 2. 



This posterior smooth groove is caused by, and lodges, the 

 Vlllth cervical nerve (Fig. 4 "nerv. cerv. VIII") as it descends over 

 the the neck of the rib on its course to enter into the formation of 

 the brachial plexus. Upon the under side of the neck of the rib is 

 a corresponding smooth area, caused by the contact of the 1st dorsal 

 nerve as it runs up, under cover of the neck of the rib, to join the 

 Vlllth cervical nerve (Fig. 4 "nerv. dors. I".) 



These two nerve roots embrace the neck of the first rib, and 

 each impresses upon it the smooth area found on the dried bone. 

 The trunk thus formed opposite the neck of the first rib ("trunc. 

 inf. plex. brachialis", Fig. 2) runs forwards and outwards along the 

 outer margin of the Scalenus minimus of Albinus, the fascial ex- 



