316 GENERAL ANATOMY. 



vessels with a peculiar membranous envelope, still compre- 

 hended many different parts, and supposed an exact know- 

 ledge of the intimate texture. 



It has also been attempted to define the glands by their func- 

 tion, by saying that they are secreting organs; but by after- 

 wards confounding nutrition and secretion, the greater number 

 of the organs were included in this definition; or by distinguish- 

 ing these functions from each other, but not separating intrinsic 

 from excretory secretions, the serous and synovial membranes 

 were confounded with the glands. 



In order to distinguish the glands from all other parts ana- 

 logous to them in form, in apparent texture, and even to 

 a certain extent in functions, we must take particular notice 

 of their connexions; Bichat and Chaussier have taken this 

 consideration for the basis of a definition of the glands; Haase 

 has likewise adopted it; but he has supposed excretory ducts 

 to the vascular ganglions. The glands are organs of an ob- 

 round lobular form, surrounded with membranes, having many 

 vessels and nerves, and provided with ramified excretory 

 canals which terminate at the surface of the tegumentary 

 membranes and pour out a secreted liquid. Finally, these 

 are the organs of extrinsic secretions furnished with excreto- 

 ry ducts. 



479. The glands, when thus considered, are mere appen- 

 dages or prolongations of the tegumentary membranes. In 

 animals provided with vessels and a heart, the only ones which 

 have massive glands, they result from the intimate reunion of 

 these two kinds of organs: this is the reason why their de- 

 scription is placed here. They belong, however, more to the 

 tegumentary than to the vascular system, for in animals de- 

 prived of vessels, glands exist, but in a rudimentary state; 

 the liver, the most constant of all the glands, the kidneys ex- 

 cepted, exists, in fact, in insects under the form of a ramified 

 excretory canal, terminating in the intestinal tube, but floating 

 and free in the abdomen. 



480. It is also pretty difficult, and perhaps impossible, to 

 establish a well marked line of distinction between the folli- 

 cles or crypta? and the glands. 



