THYREOID GLAND 319 



it passes posterior or anterior to the subclavian artery ; on 

 the left side it is continued downwards between the common 

 carotid and subclavian arteries. 



Ganglion Cervicale Inferius. The inferior cervical ganglion 

 is lodged in the interval between the transverse process of the 

 seventh cervical vertebra and the neck of the first rib. In this 

 position it lies posterior to the vertebral artery. It is by no 

 means uncommon to find it more or less completely fused, 

 over the neck of the first rib, with the first thoracic ganglion. 

 The connection between it and the middle cervical ganglion is 

 generally in the form of two or more slender nerve cords, of 

 which one passes anterior to the subclavian artery. The 

 latter loops round the subclavian artery and is termed the 

 ansa subclavia (Vieussenii). 



The branches of the inferior cervical ganglion are : 



1. Grey rami communicantes to the seventh and eighth cervical nerves. 



2. Rami vasculares. 



3. Inferior cardiac nerve. 



The rami vasculares are fine branches which form a plexus 

 around the subclavian artery and its branches. Those 

 around the vertebral artery are remarkable for their large size. 



The nervus cardiacus inferior on both sides enters the deep 

 cardiac plexus. 



After the vessels and nerves of the neck have been studied 

 the dissectors should examine the thyreoid gland. 



Glandula Thyreoidea. The thyreoid gland is a highly 

 vascular solid body, which clasps the upper part of the 

 trachea and extends upwards for some distance upon each 

 side of the larynx. It varies greatly in size in different in- 

 dividuals ; and in females and children it is always relatively 

 larger than in adult males. It consists of three well-marked 

 subdivisions, viz., two lateral lobes joined across the median 

 plane by the isthmus. Each lateral lobe is somewhat conical 

 in form ; its base lies at the level of the fifth or the sixth 

 tracheal ring, whilst its apex rests against the side of the 

 thyreoid cartilage. Its superficial or lateral surface is full and 

 rounded, and is clothed by the pretracheal layer of cervical 

 fascia, from which it derives a sheath ; and it is covered by the 

 sterno-thyreoid, sterno-hyoid, and omo-hyoid muscles, and by 

 the anterior border of the sterno-mastoid (Fig. 127, p. 322). 

 Its deep or medial surface is adapted to the parts upon which it 



