78 GENERAL ANATOMY OF THE GLANDULAR SYSTEM. 



are called the Lymphatic Glands ; but it is most commonly 

 appropriated to those organs which discharge a fluid different 

 from the blood. 



The structure by which mucus is secreted in some places, 

 appears to be very simple. Thus, in the Schneiderian mem- 

 brane and the urethra, there are small ducts from four to six 

 lines in length, and equal in diameter to a bristle, which appear 

 to be formed of the membrane on which they open. From 

 these ducts mucus issues to cover the surface of these mem- 

 branes. In many instances there is no substance resembling 

 that of the circumscribed glandular bodies, connected with 

 these ducts ; but the secreted fluid seems to be discharged into 

 the ducts from the small vessels on their surfaces. The ducts 

 of this nature in the urethra are denominated Lacunae. 



In some other parts of the body, the cavities into which 

 mucus is discharged are somewhat different, both in form and 

 size, from those above mentioned, and are called Follicles. 

 These cavities are surrounded with more or less of a pulpy 

 vascular substance, which has been considered as glandular, and 

 essential to the mucous secretion. 



The circumscribed bodies, which are commonly called glands, 

 differ in their internal appearance and texture, from the other 

 parts of animals. The substance of which they consist differs 

 very much in the different glands ; and thus renders the liver, 

 kidneys, salivary glands, mammae, &x>., very different from each 

 other. Some glands, as the salivary, &c., are composed of 

 several series of lobuli that successively diminish. The smallest 

 of these are denominated Acini. Each of them is connected 

 by a small artery and vein, to the large blood-vessels of the 

 glands ; and also sends a branch to join the excretory duct. 



These Acini are therefore connected to each other, by the 

 blood-vessels and excretory duct of the gland, and also by the 

 cellular membrane which covers them externally, and occasions 

 them to adhere to each other where they are in contact. In 

 consequence of this structure, these glands have a granulated 

 appearance. 



The liver, when incised with a sharp instrument, appears 

 differently ; but when broken into pieces, it seems to consist of 



