THE EVIDENCE OF THE THYROID GLAND 1 95 



chamber, and is curled upon itself in its more posterior part. This 

 central chamber divides, anteriorly to the thyroid orifice, into two 

 portions, A, A' (Fig. 82), giving origin to two tubes, B, B', which lie 

 close alongside of, and extend further back than, the posterior limit 

 of the curled portion of the central chamber, C. The structure of 

 the central chamber, C, and, therefore, of the separate coils, is given 

 in both Schneider's and Dohrn's pictures, and is represented in 

 Tig. 81 (6), which shows the peculiar arrangement and character of 

 the glandular cells typical of this organ, and also the nature of the 

 central cavity, with the arrangement of the ciliated epithelium. The 

 structure of each of the lateral tubes, B, is different from that of the 

 central chamber, in that only half the central chamber is present 

 in them, as is seen by the comparison of the tube B with the tube C 

 in Fig. 81 (5 and 6), so that we may look upon the central chamber, 

 C, as formed of two tubes, similar in structure to the tubes B, which 

 have come together to form a single chamber by the partial absorp- 

 tion of their walls, the remains of the wall being still visible as the 

 septum, which partially divides the chamber, Q, into halves. 



In the walls of each of these tubes is situated a continuous 

 glandular line, the structure of the glandular elements being specially 

 characterized by the length of the cells, by the large spherical nucleus 

 situated at the very base of each cell, and by the way in which the 

 cells form a wedge-shaped group, the thin points of all the wedge- 

 shaped cells coming together so as to form a continuous line along 

 the chamber wall. This free termination of the cells of the glaud 

 in the lumen of the chamber constitutes the whole method for the 

 secretion of the gland ; there is no duct, no alveolus, nothing but this 

 free termination of the cells. 



Moreover, sections through the portion A, A' (Fig. 82) show that 

 here, as in the central chamber, C, four of these glandular lines open 

 into a common chamber, but they are not the same four as in the case 

 of the central chamber, for if we name these glandular lines on the left 

 side a b, a V (Fig. 81), and on the right side c d, c' d', then the central 

 chamber has opening into it the glands a b,c d, while the chambers of 

 A and A' have opening into them respectively a b, a' V, and c d, c' d'. 

 Further, the same series of sections shows that the glands a and b are 

 continuous with the glands a' and b' respectively across the apex of A, 

 and similarly on the other side, so that the two glandular rows a b 

 are continuous with the two glandular rows a' //, and we see that the 



