, 790 



HI/MAN ANATOMY. 



i_ .Epiglottis 



,t the thyroid. i> f.mn.l mire or Lea developed in probably half the cases A M Jical 

 one reach,, the hyoid bone, to the body of which die process is generally attached 

 either by muscle or ligament. It is rarely quit, median, being more frequently found 

 S the "lei, : * its frequency vary greatly ^eckeisen ^ys^is 



FlG I5I0 . 20 per cent. ; but, since goitre 



is common in Switzerland, his 

 sources of information are not 

 of the best. Zuckerkandl, 



V however, puts the occurrence 



I S !^\__superiorconiuof of the process at 74 per cent. 



If -A\ thyroid cartilage Gruber, in Russia, found it in 



jjjk only 40 per cent., and Mar- 



shall, in England, in 43 per 

 cent. We incline to believe 

 that these latter figures rep- 

 resent the more common pro- 

 portion. 



The thyroid lies beneath 

 the group of infrahyoid mus- 

 cles, from which it is separated 

 by the middle layer of the 

 cervical fascia. The sterno- 

 mastoid muscle crosses the 

 lower part of the lateral lobes. 

 The inner surface lies against 

 the trachea, the cricoid carti- 

 lage, and the lower posterior 

 part of the wings of the thy- 

 roid cartilage. It reaches back 

 to the oesophagus, which it 

 touches on the left, and some- 

 times on the right also. It 

 may touch the lower part of 

 the pharynx on both sides. 

 The sheath of the carotid lies 

 against the posterior surface- at 

 its outer border and is in part 

 external to the organ. The 

 common carotid is usually be- 

 hind the thyroid and the inter- 

 nal jugular vein beyond it. 

 This explains how an enlarged 

 gland insinuates itself between 

 these vessel -v Frozen sections show that often the carotid is external rather than 

 poMeri.u- t<> the organ, but still in close relation to it. Internal to the carotid 

 sheath, it rests b hind against th, piwertebral fascia. The inferior thyroid arteries 

 -ntT tin- I.iti-r.il lobes from the inner side and th, superior thyroid arteries from the 

 antiToiAtiTii.il. Th, middle cervical sympathetic ganglion is behind. The inferior 

 laivngeal nerves lie at its inner surface, the left one being in actual contact with the 

 iluroid and the right ..n<- at lea>t very dose to it. The sheath connects the thyroid 

 IM..IV very elos.-K t.i neig hi x .t 'ing parts. It is so firmly bound to the trachea as to 

 follow its mo\einent-v Median bands to the cricoid and thyroid cartilages have been 



1 Marshall Journal of Anatomy and Physiology, vol. xxix., 1895. 

 1 's Anliiv, |',.l. ciii., 1886. 



.Occasional foramen 



.Thyroid cartilage 



.Crico-thyroid 

 membrane 



.Cru-o-thyroid 



muscle 

 .Cricoid 



cartilage 

 Suspensory 



ligament 

 'yramidal 



process 



isthmus 



Lobule 



llui. '<; anterior aspect. 



