582 
ME. E. C. BABER OX THE STRUCTURE OF THE THYROID GLAR’D. 
MICROSCOPIC APPEARANCES. 
Speaking generally, the only points in regard to the histology of the thyroid gland, 
on which recent authors appear to be unanimous, are, that it consists of “ cavities ” 
lined by a single layer of epithelium and held together by a more or less dense stroma 
of connective tissue. Further, that numerous blood-vessels and lymphatics, also 
nerves, are found in the stroma, and that the whole organ is surrounded by a capsule 
of connective tissue, which is continuous with the stroma in its interior. On other 
points, such as the shape of these “ cavities ” (vesicles), the character of their epithe¬ 
lium, the nature of the contents of the vesicles, &c., the opinions of authors are at 
variance. In considering these subjects in order, it will be convenient to discuss 
them under the following heads. 
I. Vesicles. 
Literature .—The majority of observers {e.g., Henle, Kolliker, Verson, Frey, and 
Leydig) have described the vesicles of the thyroid gland as consisting of closed globular 
bodies, not communicating with one another. Virchow, and more recently Boechat 
and Zeiss, however, believe that this is not the case, but that the supposed closed 
globular bodies form a system of branched cavities in the gland. Virchow {op. cit., 
p. 201) finds that the apparently vesicular bodies are in multiple connection with one 
another. Boechat {op. cit., p. 43) considers that all the cavities of the thyroid gland 
communicate with one another. Zeiss {op. cit., p. 14) does not go to this length, but 
maintains that in the thyroid gland of young Children, of the Calf, of young Dogs and 
Sheep, a not insignificant part of the parenchyma is made up of branched cavities 
(branched tubes) ; but whether these all communicate with one another, and whether 
completely closed vesicles also occur, he leaves undecided. Both Boechat and Zeiss 
endeavoured to prove the existence of these branched cavities by injections by the 
method of puncture, but without success. Their failure they attribute to the injecting 
fluid entering the large spaces of the lymphatics or blood-vessels in preference to the 
branched cavities, which, as Zeiss points out, are filled partly with an easily coagulable, 
albuminous fluid and partly with the viscid colloid material. Although this observer 
has traced the epithelial layer running from one vesicle to another, he has never 
observed tubes passing from one lobule of the gland to another. Zeiss demonstrated 
these tubes by floating them out in a solution of common salt from small portions of 
the fresh gland of young animals, also after maceration in iodised serum or in dilute 
Muller’s fluid. Circular, oval, conical, or pyramidal cavities were thus obtained 
together with long tubes, sometimes extending “ right across the field of the microscope, 
having a narrow, wide, or irregular lumen, which divide and branch, and are provided 
at intervals with lateral protuberances or constrictions.” He considers that the tubes, 
so plainly seen by isolation or maceration, are rendered invisible in sections by the 
circumstance that they interlace so freely in all directions that in a section they must 
