DUCTLESS GLANDS. 359 



Sequard. Dr. Harley, also, in one of the experiments 

 in which the animal died, failed to find pigmentary mat- 

 ter. 1 



In view of these facts, and in the absence of comparative 

 examinations of the blood going to the suprarenal capsules 

 by the arteries and returned from them by the veins, it is 

 impossible to assign any definite function to these bodies, and 

 it is certain that they are not essential to life. Their greater 

 relative size before birth has led to the supposition that they 

 might have an important office in intra-uterine life, but this 

 is a pure hypothesis, based upon no positive knowledge. 



Thyroid Gland. 



The history of this gland belongs almost exclusively to 

 descriptive anatomy ; and its only physiological interest is 

 in the similarity of its structure to that of the other ductless 

 glands. It has no excretory duct. It is attached to the 

 lower part of the larynx, following it in its various move- 

 ments. Its color is brownish-red. The anterior face is con- 

 vex, and is covered by certain of the muscles of the neck. 

 The posterior surface is concave, and is applied to the larynx 

 and trachea. It is formed of two lateral lobes, with a rounded, 

 thickened base below, and a long, pointed extremity extend- 

 ing upward, connected by an isthmus. Each of these lobes 

 is about two inches in length, three-quarters of an inch in 

 breadth, and about the same in thickness at its thickest por- 

 tion. The isthmus connects the lower portion of the lateral 

 lobes. It covers the second and third tracheal rings, and is 

 about half an inch wide and one-third of an inch thick. From 

 the left side of the isthmus, and sometimes from the left lobe, 

 is a portion projecting upward, called the pyramid. The 

 weight of the thyroid gland, according to Sappey, is from 

 three hundred and fifty to three hundred and eighty grains. 

 It is usually stated by anatomical writers that it is relatively 



1 Loc. dt. 



