MORPHOGENESIS OF THE FOLLICLES 



421 



to 22 mm. in length. (Numbers 3, 4, 5, 6, 7, 8,, 9, 10, 11, 12, 

 13, 14, 15, 16, 17, 18 of the present series.) 



Such a description, however, does not apply to the so-called 

 lateral thyroid anlage (ultimobranchial body). As described by 

 Tourneaux and Verdun ('97) and others, this body long remains 



M66. 



Fig. 1 Semi-diagrammatic drawing (camera lucida outlines) of a trans- 

 verse section through the left lateral lobe of the thyroid gland and neighboring 

 .structures from a human fetus 22 mm. long (No. 18). This shows the complex 

 interrelation of the smooth epithelial plates (PI.) (which appear as 'cords' in 

 the section) and the vascular mesenchyme (Mes.) found in the interspaces be- 

 tween them. The apparently detached epithelial masses (Ma.) shown are sec- 

 tions through projections from plates located in the upper part of the isthmus 

 of the gland. B.V., blood vessel; M., muscle; L., larynx; C, cartilage. X 133. 



as a compact, deeply staining mass of epithelium (the 4nner 

 condensation' of Kingsbury '14) on the dorso-medial aspect of 

 each lateral lobe. Whether in the human thyroid the lateral 

 anlage later atrophies or finally becomes transformed into per- 



