226 



OF ABSORPTION AND SANGUIFICATION. 



elongated spaces imbedded in the trabeculre and capsule of the gland. The 

 chemical constituents of the TItymus are water, albumen, gelatin, sugar, fats, 

 leuciu, and sarkiu, with xauthic, formic, acetic, succinic, and lactic acids, 

 and the ordinary inorganic salts. 1 The expressed juice of the Thymus 

 (Fig. 99) in young and healthy animals possesses a creamy consistence and 

 opacity due to the great abundance of corpuscles or free nuclei, identical in 

 size, shape, and chemical characters with the corpuscles of the fluid of the 

 lymphatic and mesenteric glands. The nerves are not very numerous, but 

 were observed by Peremeschko partly to accompany the arteries, and in part 

 to enter separately. Mr. Simon considers that they are mainly derived from 

 the plexus which surrounds the first part of the subclavian artery, and which 

 has its chief origin from the inferior and middle cervical ganglia. It has 

 been commonly stated, that the Thymus attains its greatest development in 

 relation to the rest of the body, during the latter part of fetal life ; and it 

 has been considered as an organ peculiarly connected with the embryonic 

 condition. But this is a mistake ; for the greatest activity in the growth of 

 this organ manifests itself, in the Human infant, soon after birth ; and it is 

 then, too, that its functional energy seems the highest. This rapid state of 

 growth, however, soon subsides into one of less activity, which merely serves 

 to keep up its proportion to the rest of the body ; but its increase is continuous 

 till the age of puberty is attained (Friedleben). From that time, during a 

 variable number of years, it remains stationary in point of size ; but, if the 

 individual be adequately nourished, it gradually assumes the character of a 

 mass of fat, by the development of the corpuscles of its interior into fat-cells, 

 which secrete adipose matter for the blood. This change in its function 



is most remarkable in hibernating 

 Mammals; in which the development 

 of the organ continues, even in an 

 increasing ratio, until the animal 

 reaches adult age, when it includes a 

 large quantity of fatty matter. The 

 same is the case, generally speaking, 

 among Reptiles. 



164. The Thyroid body differs from 

 the other Vascular Glands in its ele- 

 mentary structures ; for it essentially 

 consists of an aggregation of vesicles 2 

 (Fig. 100, b, b\ which seem to be furn- 

 ished with a true limitary membrane, 

 and therefore to be real gland-vesi- 

 cles, imbedded in a stroma (a, a) of 

 connective tissue, which supports a 

 vast cavernous lymphatic network. 

 The vesicles vary in diameter, in 

 the Human subject from ^' ^th 

 to ^T-th of an inch ; and they con- 

 tain an albuminoid plasma, 3 of either 



FIG. 100. 



Group of gland-vesicles from the Thyroid Gland 



of ;i rliil'l : a, ruiiiiei'tivi' tissue; li, membrane of 

 the vrMi'lrs; c, epithelial cells. 



1 See Friedlebcn, in the Journal de la Physiologic, 18o9, p. 137; and v. Gorup- 

 I'.'-sanez, IMiys. Cliemie, 18<>2, p fiCil. 



2 Tln'.-<- vc.-icli-s \vrc formerly stated to bo closed, but P. A. Roe'ehat (Central- 

 hlatt, 1S7I, |i HI) ha< recently maintained, as the, result of observations made upon 

 liealtliy glands hardened in I'icric Acid, subsequently placed in solution of gum, and 

 finally in alcohol, that they intercommunicate freely. 



3 That the fluid does nut contain true Albumen in solution, hut some albuminous 

 cMinpniind.-, is indicated by the results of Dr. Beule's analysis (Cyclop, of Anat. and 

 Physiol., vol iv, p. 1100)! 



