416 EDGAR H. NORRIS 



distributed throughout the gland. Some branching vesicles 

 were also noted at 17.5 cm. 



Prenant ('01) (p. 13) stated that in the embryonic thyroid the 

 solid epithelial cords are transformed into a network of tubes 

 from which the follicles arise by a process of constriction. 



Von Ebner('02) found numerous well developed follicles in 

 older fetuses and newborn. Between the foUicles are found, 

 even in the adult, frequent solid strings and nests of epithehal 

 cells, which are in the majority during development. 



Elkes ('03); who studied the thyroid in fetuses from four and 

 one-half to six and one-half months in age, found that it pre- 

 sents both solid cords and well developed follicles in variable 

 number. In the new-born the earlier follicles have largely 

 disappeared, leaving only a few at the periphery of the gland. 



Hertwig ('10) (pp. 444-446) described in the embryonic thy- 

 roid anastomosing epithehal cylinders. These become tubular; 

 varicose dilations are by ingrow^th of the adjacent connective 

 tissue cut off to form the permanant folhcles. 



Isenschmid ('10) found that in the thyroid of children the 

 gland growls not only by the increase in the size of the follicles, 

 but by the formation of new folhcles by two methods: budding 

 and division. He found no evidence that folhcles are formed 

 from solid cell-masses (interfolhcular epithehum) retained from 

 the embryonal period. 



According to Hesselberg ('10): "Die Ausbildung der Thy- 

 reoidea in der fotalen Periode erfolgt durch Zerfall der ursprung- 

 hch sohden Zellplatte in solide Zellstriinge. Diese schntiren 

 sich zu Blaschen ab, die zuerst am kaudalen Pol auftreten." 

 The normal structiu-e of the thyroid is established from the 

 fourth fetal month on. Desquamation of epithehal cells was 

 found in about half of the cases from the seventh to the ninth 

 fetal month, and the folhcles are almost entirely obliterated in 

 the newborn. During the first week of postnatal hfe the fol- 

 licles are reformed and increase in number by a process of 

 budding. 



Prenant and Bouin ('11) give an account of the development 

 of the median thyroid anlage similar to that given by Pre- 

 nant ('01). 



