The Pathological Anatomy and 

 Histology of the Thyroid 



DAVID MAKIKE 



NEW YORK 



Introduction 



The thyroid gland is one of the oldest and most constant organs of 

 Chordates. It exists as the "endostyle organ" in the lowest of Chordates 

 the Tunicates, in Amphioxus and in Ammoeoetes (larval lampreys). 

 Owing to a curious biological preservation the Ammocoete combines in its 

 life cycle both the endostyle organ and the ductless thyroid. The dis- 



Fig. 1. Cross section of endostyle organ 

 of Holocynthia johnsonii with adjacent 

 parts of branchial (pharyngeal) sac. 

 (After Marine, Johns Hopkins Hosp. Bull., 

 1913: 24.) 



Fig. 2. Cross section of endostyle organ 

 of Amphioxus calif., showing its relation 

 to branchial (pharyngeal) sac and gill 

 filaments. (After Marine, Johns Hopkins 

 Hosp. Bull., 1013: 24.) 



appearance of the endostyle and the development of the ductless thyroid 

 alveoli from definite groups of cells of the endostyle has been carefully 

 studied during the metamorphosis of the Ammocoet (see Figs. 1, 2, 3, 4). 

 We are at present concerned only with the ductless thyroid. Morpholog- 

 ically it is one of the simplest of body tissues and resembles more closely 



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