738 SPECIAL PHYSIOLOGY. 



plasma, containing nuclei and certain cells, the latter resembling the 

 ganglionic cells of gray nervous substance (Leydig, Kblliker). The 

 arteries, numerous and small, reach the suprarenal bodies at many 

 points of their surface, and ramify between the rows of loculi, ending 

 in capillary networks around them. The veins, also numerous, are 

 collected into a plexus in the centre of the organ, where a venous 

 sinus, sometimes taken for a gland cavity, is found. The lymphatics 

 are said to be not very numerous. The nerves, however, are very 

 large, and are derived chiefly from the sympathetic, but also in part 

 from fibres of the pneumogastric and phrenic nerves. 



From the quantity of blood received by the suprarenal bodies, and 

 from the number and character of their microscopic elements, it is evi- 

 dent that the nutritive processes which take place within them are 

 very active. Probably, like the spleen, they modify the blood passing 

 through them, by subtracting from it, and returning to it, certain 

 materials in an altered form ; but their precise function is unknown, 

 whether this be entirely elaborative, or partly destructive. A curious 

 bronzed color of parts of the skin, has been frequently seen in disease 

 of the suprarenal capsules (Addison, Hutchinson); but cases of simi- 

 lar cutaneous bronzing have been noted, in which the capsules were 

 healthy (Parkes, Harley) ; moreover, these organs have been found 

 diseased without bronzing of the skin (Kirkes, Day, Hutchinson). 

 From the numerous cells, like ganglionic cells, in the medullary por- 

 tion of these bodies, it has been suggested that this part may consti- 

 tute a nervous apparatus, or be nutritively connected with the nervous 

 system. 



The Pituitary Body. The posterior lobe of this body (p. 243) con- 

 sists of true nervous substance ; but its anterior lobe is composed of 

 an areolar framework, forming loculi or spaces, which contain a granu- 

 iar plasma, nuclei, and nucleated cells of various forms, a structure 

 somewhat, though not precisely, like that of the cortical part of the 

 suprarenal capsules, or the vesicles of the thyroid body. It may, 

 therefore, be temporarily classified with the ductless glands, though 

 not from any established identity or similarity of function, which is 

 wholly unknown. 



The Thyroid Body. This body, commonly named the thyroid gland, 

 is a soft, reddish-brown, vascular organ, placed upon the front and sides 

 of the upper part of the trachea, and reaching upwards to the sides of 

 the larynx, to which it is suspended. It is formed of two lateral, 

 somewhat pyriform lobes, joined together, at their lower and larger 

 ends, by a transverse part, named the isthmus. The lobes are about 

 :2 inches long, and measure } of an inch in their thickest part. The 

 ithyroid body varies in weight from 1 to 2 ounces ; it is larger in the 

 female than in the male. 



The thyroid body differs in structure from the other ductless glands, 

 inasmuch as its proper tunic and framework of areolar tissue, forms 

 loculi, in which are embedded multitudes of rounded closed vesicles, 

 bounded by a distinct membrana propria, and lined by an epithelium. 

 The vesicles, which measure from jfl^ffth to g^th of an inch in diame- 

 ter,, contain a viscid, clear, albuminous fluid, in which are found nuclei 



