-51- 



thyroid whloh necessitates' the very deep ciliated groove shovm 

 in this and the next figure. The arteries (art.) -re very large 

 and are bound closely to the gland by the connective tissue men- 

 tioned above. The cover layer (d.l.) in these sections is re- 

 duced to such a thin membrane that it is often difficult to dis- 

 tinguish it from the connective tissue to which it is closely 

 applied throughout. 



A section passing directly through the opening of the 

 duct into the gland is represented in Fig. 6 c. The duct, a 

 deep, narrow slit, is lineal with short, ciliated columnar cells, 

 similar to, the shorter cells of the ciliated layer spoken of 

 above. These short cells lead quite sudJenl:' into the long oells 

 of the ciliated layer (f.l.). 



The lateral pair of cell-groups (l.c.g.) is now entire- 

 ly distinct from the median pair (m.c.g.), and the pocket (p.) 

 by which the lateral cell-groups are connected with the duct, 

 as before explained, is continued to the extreme posterior end 

 of the gland, the two lateral pairs of cell-groups taking no 

 part in the posterior coil but continuing back of this for some 

 distance (Figs. 6 i and k) . 



TTie median lamella (m.l.), which back to this point 

 has completely divided the gland into two parts, is, from this 

 point, merely r. tall ridge (Fig. 6 c, m.l.) projecting up'.Yards 

 into the median ciliated chamber (m.c.h.) and covered by the 

 cover cells (d.l.) (Deoklamelle) of the two median pairs of cell- 



