40 GUY DAVENPORT LOMBARD. 



ment of an almost orange hue. The organ is almost sheet-like 

 in its thinness. A dogfish of 115 cm. had a thyroid gland 

 measuring antero-posteriorly 19 mm., from side to side 42 mm., 

 and in thickness i mm. ; it weighed 502.5 milligrams. 



The thyroid gland is approximately unilobular, yet shows some 

 evidence of beginning lobulization. In addition to an almost 

 separate posterior portion it often has in its main body certain 

 indications of a tendency to further lobular subdivision formed 

 by interruptions of the glandular tissue which are filled in by 

 septa or trabeculae of loose connective tissue. There may be 

 three incisures of this sort, all beginning at the posterior border 

 of the main portion of the gland and extending, almost at right 

 angles to the border, into the glandular substance. The most 



Fig. I. Outline of the thyroid gland of a dogfish as viewed from the ventral sur- 

 face, showing the distribution of its arterial supply. The dotted lines indicate an area 

 over which the thyroid substance was deficient, a, right (dorsal) thyroid artery ; b, 

 left (ventral) thyroid artery. 



constant of these fissures, and the largest, is situated in the 

 median line ; a smaller indentation is often observed on either 

 side of this primary one, almost parallel to it, and so placed as to 

 be approximately equidistant between the primary fissure and 

 the lateral border of the gland. 



The smaller fissures may vary in extent, but the one on the 

 right of the median line is nearly always shorter than that on the 

 left. This difference is readily understood by a reference to the 

 anatomical relation of the right thyroid artery to this portion of 



