THE DUCTLESS GLANDS GENERALLY. 743 



occasional opening of the loculi into the veins, as in the spleen, or into 

 the lymphatics, as conjectured by some to be the case in the thymus. 



By both subtraction and addition of material, the blood must be 

 specially modified, as it passes through those organs, which, from their 

 various actions, contribute, therefore, to the elaboration and mainte- 

 nance of the complex chemical constitution of the blood. It is for the 

 preparation of the albuminoid constituents of the blood, that these 

 organs are destined, and not for the formation of fatty matter, which 

 is so scanty in their composition. Their action upon the coloring mat- 

 ters, which are also albuminoid, may be, in the case of the spleen and 

 suprarenal bodies, to decompose or re-compose those peculiar sub- 

 stances. Moreover, from the resemblance of the microscopical elements 

 of their abundant and characteristic parenchyma, to the white blood- 

 corpuscles, they are probably concerned in the formation of those 

 bodies, and therefore of the future red corpuscles, assimilating the 

 nutrient plasma of the blood into distinct morphological elements, just 

 as the lymphatic glands and vessels develop a corpusculated fluid in 

 their interior. Hence, both chemically and morphologically, the blood 

 glands are believed to contribute to the important process of sanguifi- 

 cation. The products of nutrient secretion formed by these organs 

 all enter the systemic veins, excepting those elaborated by the spleen, 

 wbich first enter the portal blood, and so pass through the liver, before 

 they reach the right side of the heart, to be sent to the lungs. 



It is remarkable that all the large ductless glands are present and 

 active during embryonic life, and also in the most active period of 

 growth after birth. The suprarenal bodies at first, in the embryo, 

 much larger than the kidneys, are, in the adult, only jgth part of the 

 weight of those glands. The thymus especially ceases, after birth, to 

 grow in proportion to the rest of the body, and then gradually wastes ; 

 a positive relation has been observed in young animals, between its 

 size and the state of their nutrition. The thyroid body and the pitui- 

 tary body are also larger proportionally in the embryo and the infant, 

 than in the adult ; but they continue to be present throughout life. 

 At birth, the weight of the thyroid body, as compared with that of the 

 body generally, is as 1 to 250 or 1 to 400 ; but it soon ceases to en- 

 large with the body, for, after three weeks, the proportions are as 1 to 

 1166, and in the adult only as 1 to 1800 (Krause). The spleen, how- 

 ever, enlarges with the body, and maintains its proportionate size ; 

 but it is undoubtedly largest in the most active period of life, about 

 early manhood. As to the closed sacs of the tonsils, tongue, pharynx, 

 and solitary and agminated glands of the stomach and intestjne, they 

 exhibit a continuous development with the rest of the body, and are 

 permanent structures. 



Finally, it would seem that, whatever may be the general or special 

 uses of the ductless glands, some of them, at least, are not absolutely 

 essential to life. The thymus, though very large in the early period 

 of development and growth, ultimately disappears as a distinct organ. 

 The thyroid body may be totally altered by disease, becoming cystic, 

 indurated, or filled with earthy deposits, without serious detriment to 

 the health. The spleen has been extirpated from animals, without any 



