130 



TWELFTH LECTURE. 



propria serves for the transudation and filtration of the blood 



plasma. 



. . . * 



Its origin takes place in the nature of a boundary layer, 



formed from the adjacent connective tissue. 



The form of the gland or of its constituents 

 is determined by the membrana propria, or the 

 connective tissue, by which it is frequently re- 

 placed. For the organ may, with microscopic 

 dimensions, remain very simple, while, on the 

 Other hand (think of the liver and kidney), 

 with an increased size, it may assume the most 

 complicated structure. 



We distinguish : 



I. The tubular glands (Fig. 117). Here, 

 the membrana propria forms a caecal tube, 

 generally of considerable length and of rela- 

 tively slight diameter. Several such ceecal 

 tubes, invisible to the naked eye, may come 

 together in a common terminal portion, so 

 that there is always a more distinct excretory 

 duct. 



Extraordinarily long reticular and caecal Cle- 

 ric 119. — Aeon- J ° 



voimcd gland from me nts, w^ith many peculiarities, united in im- 



the conjunctiva of •? * 



lhe calf - mense numbers, constitute the testicle and 



kidney. We speak now of the tubular glands. 



Another modification is formed by the so-called convo- 

 luted glands (Fig. 119). The terminal portion of this small 

 organ presents a peculiar convolution like the coil of a pack 

 thread. 



2. Another uncommonly diffused form is the racemose 

 gland (Fig. 120). The membrana propria here appears as a 

 microscopically small, rounded, elongated or irregularly 

 formed saccule." These " gland vesicles " are united at their 

 openings in groups, and in this manner a lobule or acinus is 



* It has been proposed to include the small racemose structures of the mucous 

 membrane among the ;< tubular" glands, on account of their elongated saccules. 



