THE THYROID AND PARATHYROIDS 263 



the thyroid, and another on the mesial surface of each lateral 

 lobe ('inner epithelial body')." 



Despite this confusion in terminology, for most animals, 

 at any rate, the terms " external " and " internal " are suffi- 

 ciently suitable for designating the two parathyroids respect- 

 ively ("III" and "IV"), because it so happens, that the 

 glandule which lies on the surface of the gland lies also in the 

 majority of cases on the lateral aspect of the lobe, and the one 

 which is buried in the thyroid substance is nearer the mesial 

 surface. 



(6) In Man the anatomy of the thyroid is too well 

 known to need any description. It belongs to the group of 



FIG. 58. Semi-diagrammatic sketch 

 showing the position of the parathy- 

 roids, the thyroid, and the trachea 

 in the human subj ect. Front view. 

 Parathyroids projected on to the 

 surface. 



FIG. 59. Semi-diagrammatic sketch 

 showing the position of the para- 

 thyroids in the human subject. 

 Posterior view. 



thyroids possessing an isthmus. There are many points of 

 interest, embryological and surgical, connected with some 

 common varieties, but there will not be space to treat of these. 

 The parathyroids, according to most observers, are four in 

 number two on each side of the median line of the body. 

 The average dimensions are about 6 or 7 millimetres in length, 

 3 or 4 millimetres in breadth, and 1'5 or 2 millimetres in 

 thickness. The length is very variable, while the thickness 

 is fairly constant. In shape they are oval or pyriform, and 



