264 THE DUCTLESS GLANDS 



they may be connected by a stalk, in which run the para- 

 thyroid vessels, to the thyroid gland. The average weight 

 is 0*035 gramme. There seems to be no relation between 

 the weight of the parathyroids and that of the thyroids. 

 The parathyroids are of a lighter colour than the thyroids, 

 and yellowish owing to the presence of fat. The surface is 

 smooth and soft. 



The two glands on each side are described under the names 

 of the "posterior superior parathyroid," and an "anterior 

 inferior " parathyroid, the names indicating their relation to 

 each other. (See Figs. 58 and 59.) The posterior superior 

 glandule is more constant in position than the anterior inferior. 

 It lies usually on the posterior wall of the oesophagus or pharynx 

 at the level of the lower edge of the cricoid cartilage, imme- 

 diately internal to the posterior margin of the lateral thyroid 

 lobe, and in front of the prevertebral division of the cervical 

 fascia. The parathyroid is usually separated from the thyroid 

 by a septum of connective tissue. 



The anterior inf erior^hyroids are very inconstant in position 

 and relations. Sometimes their position is more anterior, 

 sometimes more posterior, and they may, especially in the 

 former case, be placed very low down, even at the level of the 

 tenth tracheal ring. 



(c) Monkey. The writer is not acquainted with any descrip- 

 tion of the parathyroids in the anthropoid apes. In the 

 different species of monkey usually employed for operations 

 in the laboratory, the arrangement of the parathyroids is 

 quite different from that in the human subject. The present 

 writer, working in conjunction with Professor W. A. Jolly, 

 found that in the monkey the thyroid lobes are sometimes 

 united by an isthmus, sometimes unconnected. There is a 

 well-developed isthmus in Macacus rhesus, and the parathyroids 

 are four in number, two on each side, and are always, so far 

 as we have seen, embedded in the substance of the thyroid. 



(d) Dog. The thyroid of the dog usually consists of two 

 distinct lobes unconnected by any isthmus. Ellenberger and 

 Baum, however, state that the thyroid consists of two lateral 

 lobes and an isthmus, which latter structure is wanting in 

 small dogs and present in large ones, while in dogs of medium 

 size it is sometimes present. The lateral lobes are elongated, 

 oval, and taper slightly at oral and aboral ends. They are 



