Chick Embryo Thyroid 



173 



Fig. 2. Section through the basal part of a thyroid cell and a capillary showing endothelial discontinuities. BM = base- 

 ment membrane: END -■^- endothelium: RB -- red blood corpuscle. Magnification 62,C00. 



more or less distinct fairly dense membrane and the 

 endothelial basement membrane continues uninter- 

 rupted over these areas. The width of the discon- 

 tinuities is about 300 A. 



References 



1. Braunsteiner, H., Fellinger, K., and Pakesch, F., 

 Endocrinology 53, 123 (1953). 



2. Dempsey, E. W. and Pi n rson, R. R., Endociinoloi;y 36, 



46 (1955). 



3. Ekholm, R. and Zelander, T., Experientia 12. 195 ( 1956). 



4. Monroe, B. G., Anat. Rec. 116, 345 (1953). 



5. Newman, S. B., Borysko, E., and Swerdiow, M., J. 



Research Natl. Bur. Standards 42,, 183 (1949). 



6. Palade, G. E., J. E.xptl. Med. 95. 285 (1952). 



7. Sjostrand, F. S., Experientia 9, 114 (1953). 



8. — //( PoLLiSTER, A. W., Physical techniques in biological 



research. Vol. III. New York, 1956. 



Electron Microscopy of Chick Embryo Thyroi(d 

 R. Stole, P. Blanquet, A. P. Lachapele, R. Maraud, and A. Magimel 



Fondation Bergonie and Facidte de Medecine, Bordeaux 



According to a previous investigation the differ- 

 entiation of the chick embryo thyroid shows two 

 successive periods (18). In the first one, before 12 

 days, the thyroid anlage concentrates very low quan- 

 tities of radioiodine and is practically devoid of 

 follicles. During the second one, the uptake of radio- 

 iodine raises suddenly and strongly together with 

 the differentiation of the follicular structure. Differ- 



ence between the two periods is closely associated 

 with colloid synthesis. 



The present investigation was undertaken to de- 

 termine to what extent this phenomenon could be 

 related to the development of the c\toplasmic cana- 

 licular structures which were described in the thyroid 

 of adult mammals (4, 14. 15. 23. 24). 



Normal thyroid glands were obtained from 36 embryos 



