146 LECTURE VI. 



coat, and lying on this is found, in the last place, a flat, 

 extremely translucent layer of epithelium, which is very 

 prone to protrude out of the cut end of the vessel, and 

 gives the impression of spindle-shaped cells, so that it 

 may easily be mistaken for spindle-shaped muscular cells. 

 The smallest veins likewise possess this epithelium, but, 

 with this exception, are, properly speaking, entirely com- 

 posed of connective tissue provided with longitudinal 

 nuclei (Fig. 45, v). 



These relations undergo no essential change even when 

 the individual constituents of the vascular system expe- 

 rience the most extreme enlargement. This is best seen 

 in pregnancy, in which not merely in the uterus, but also 

 in the vagina, the Fallopian tubes, the ovaries, and the 

 ligaments of the uturus, both the large and small arteries 

 and veins, as well as the capillaries, exhibit a very high 

 degree of dilatation, so that the rest of the tissue, in spite 

 of its having likewise in no inconsiderable degree become 

 enlarged, is thereby virtually thrust into the back- 

 ground. Nevertheless, however, parts of this puerperal 

 sexual apparatus are extremely well adapted for display- 

 ing the relation between the histological elements and 

 the vascular (arterial) districts. In the fimbrise of the 

 Fallopian tubes, for example, every plexus or loop 

 formed towards the borders by the greatly dilated capil- 

 laries encloses a certain number of large connective tis- 

 sue cells, of which only a few lie in immediate contact 

 with the vessels. In the alae vespertilionum we find, 

 moreover, very beautifully displayed, a condition which 

 is of frequent occurrence in the appendages of the gene- 

 rative organs, and similar to what we lately considered 

 in the scrotum ; the vessels, namely, are accompanied 

 by flat bundles of smooth muscle in considerable quan- 

 tity which do not belong to them, but only follow the 

 course of the vessels, and in part receive the vessels 



