THE URETERS. 429 



fixed corpuscles, the inoblasts of Krause. There is no true 

 basement-membrane. Below this stratum we find a submu- 

 cous layer, which is abundantly furnished with elastic tissue, 

 and contains a few simple acinous glands with ducts having a 

 lining of cylindrical epithelium. 



The muscular coat is composed of bundles of smooth mus- 

 cle-cells forming an inner layer, with a peripheral direction of 

 its constituent anatomical elements, and an outer layer concen- 

 trically arranged. The " papillary sphincter" is but a thick- 

 ening of this latter layer. 



The external fibrous layer forms a thin connective-tissue 

 membrane, not always clearly marked here, whereas in the ure- 

 ters and bladder it is found to be well developed. 



The blood-vessels of the pelvis are derived from the renal 

 artery and vein, and form capillary networks characterized by 

 polygonal meshes. The lymphatics and nerves are found to 

 have the same distribution as in the ureters. 



THE URETERS 



have a structure which closely resembles that of the renal pel- 

 vis. The mucous membrane shows the same varieties of epithe- 

 Hum ; its connective-tissue components are similarly arranged ; 

 and the external investing membrane is composed of the same 

 kind of tissue already described. But in addition to the two 

 muscular layers^ which here attain a greater development, we 

 find a third muscle coat, so that we can now distinguish an in- 

 ternal and external longitudinal from a middle circular layer 

 of muscular elements. 



Engelmann has described a close reticulum of blood capil- 

 laries lying immediately under the epithelial stratum, but its 

 existence is made doubtful by the negative statements of other 

 authors. 



Glandular bodies are not found in the ureters. The peri- 

 pheral layer of fibrous connective- tissue possesses conspicuous 

 elastic bundles in the lower portion of the ureters. 



The distribution of the blood-vessels is like that of the pel- 

 vis already described. The lymphatics are well developed here, 

 forming several networks in the different layers of the ducts. 

 Nerves are likewise readily distinguished, some of the nerve- 



