58 Mr. E. C. Baber on the Minute Structure [Jan. 31, 



in the vesicles, and also to that described above in the lymphatics of 

 the thyroid gland of the dog and other mammalia. In the thyroid 

 gland of the rook no system of lymphatics is injected by the method 

 of pnncture, but the blood-vessels, presenting an appearance very 

 similar to those in the pigeon, become filled. Since the publication of 

 my researches on the thyroid gland of the dog, I have become ac- 

 quainted with P. A. Boechat's thesis on the structure of the thyroid 

 gland (published in 1873), in which he describes the lymphatics of 

 this organ. I regret that I was not previously aware of his researches, 

 but it is satisfactory to find that the results of our independent ob- 

 servations on this subject are very similar. 



'Epithelial Cells. — In the thyroid gland of several animals I have 

 observed in the epithelial cells numerous very fine parallel strioe, running 

 in the direction of the long axis of the cell, i.e., from the summit (or 

 free extremity) of the cell down towards its base. I can sometimes 

 trace this striation running apparently the whole length of the cell from 

 apex to base ; at other times it is only visible for a greater or less dis- 

 tance near the summit of the cell. I have observed it most clearly in 

 the thyroid glands of the skate, tortoise, pigeon, and kitten. Be- 

 tween the epithelial cells of the thyroid gland a reticulum may often 

 be observed. I have noticed it more especially in the tortoise, skate, 

 kitten, &c. Recently Otto Zeiss * has described a reticulum between 

 the .epithelial cells of the thyroid gland. 



Parenchyma. — The large round cells described in my previous paper 

 in the thyroid gland of the adult dog, and there named " parenchy- 

 matous cells," I have since observed in do^s a°:ed five and nine weeks 

 respectively. In the thyroid gland of the cat parenchymatous cells are 

 present in considerable numbers, although not nearly so numerous as 

 in the dog. Parenchymatous cells are also seen in the thyroid of the 

 rabbit. In the thyroid gland of the pigeon large groups are frequently 

 seen consisting of cells, which are larger than the adjacent epithelial 

 cells, round or oval in shape, and provided each with a single spherical 

 or oval-shaped nucleus. They resemble very much the parenchymatous 

 cells seen in the dog. 



Undeveloped Portions. — In the thyroid gland of the adult dog bodies of 

 considerable size are frequently seen, which differ entirely in structure 

 from the rest of the gland. They are rounded or flattened in shape, 

 usually situate on the surface of the organ, and possess the following 

 structure. They consist of a solid mass of more or less cylindrical rows 

 of cells, which are much convoluted and interlace in all directions. 

 Between them run capillary blood-vessels, and also probably some 

 lymphatics. These " cylinders " are composed of cells resembling epi- 

 thelial cells, columnar or cubical in shape, those on the surface of the 



# " Mikroskopische Untersnckungen uber den Ban der Schilddnise." Strassburg, 

 1877. 



