214 



NORMAL HISTOLOGY. 



pregnancy. These changes are of importance in their bearing upon 

 the pathology of the organ, and must be briefly described. 



At the menstrual period the superficial portion of the mucous 

 membrane, down to its muscular coat, suffers a degeneration, which 

 results in its disintegration and discharge, along with some blood 

 derived from the exposed and damaged vessels of small size within 

 its tissues. After this degeneration the membrane is restored by a 

 proliferation of the elements contained between the bundles of the 

 muscularis mucosie, the glands being reformed from the remnants 

 of their deep extremities. The mucous membrane slowly continues 



Section of the human uterine mucous membrane parallel to its surface. (Henle.) 1, 2, 3, 

 uterine glands in cross-section. In 2, the basement-membrane alone is represented, the 

 epithelium having fallen out of the section. 4, bloodvessel in longitudinal section. Be- 

 tween these structures is the highly cellular stroma of the mucous membrane, only the 

 nuclei of its cells being represented. 



to increase in thickness and the glands in tortuousness until the 

 next menstruation, when the same process is repeated. It will be 

 noticed that the connective tissue of the mucous membrane, in the 

 absence of pregnancy, is subject to periodical degeneration and re- 

 generation, which probably prevent its development into a mature 

 fibrous tissue with an abundance of fibrillated intercellular substance. 

 If an ovum, discharged from the ovary, becomes fertilized, the 

 menstrual cycle of changes in the superficial portion of the mucous 

 membrane of the uterus is interrupted. That portion of the mu- 

 cous membrane then undergoes extensive modifications in structure 

 during the early months of the ensuing pregnancy. The inter- 



