THE FEMALE REPRODUCTIVE ORGANS 533 



of the serous coat and the muscular wall, to all portions of the organ. 

 In the vascular layer of the muscular coat they form an extensive ^plexus 

 from which branches are distributed to the musculature and to the mu- 

 cosa, the branches to the latter penetrating nearly to the surface, where 

 they form rich, subepithelial, capillary and venous plexuses. The uterine 

 arteries, like those of the ovary, possess a peculiar, spirally tortuous 

 course. The veins accompany the arteries, but are less tortuous. 



The lymphatics of the uterus arise by anastomosing channels in the 

 mucous and muscular coats. They form a vascular plexus in the serous 

 coat and lead outward, through the lateral ligaments and pelvic connec- 

 tive tissue, to the lower lymph nodes of the lumbar region. 



The nerves of the uterus are very numerous. They include both 

 spinal and sympathetic fibers. They enter the serous coat from the 

 ganglionic pelvic plexus, and are distributed to the vascular layer of 

 the muscular coat. They there form a rich plexus, from which sympa- 

 thetic motor fibers are distributed to the musculature and to the walls of 

 the blood-vessels. 



The distribution of nerves within the mucosa has not yet been 

 thoroughly worked out. According to von Gawronsky (Arch. f. Gynakol., 

 1894) and Kostlin (Fortschr. d. Med., 1894) sensory nerve fibrils pene- 

 trate nearly to the surface and form a scanty subepithelial plexus, whence 

 are derived fibrils which terminate between the epithelial cells. 



Since the uterus is subject to extensive structural variations dependent 

 upon its functional phase and condition, it becomes important to recog- 

 nize the differential marks of the menstruating and of the pregnant 

 uterus. Besides general histologic alterations in the wall, especially in 

 the mucous and muscular layers, additional structures involved in the 

 pregnant uterus are the decidual cells and chorionic villi; these are 

 diagnostic of pregnancy. Only the histology of these structures will be 

 here described ; for a consideration of their embryologic significance and 

 relationship reference must be made to a text-book of Embryology. 



The Menstruating Uterus 



The appearance of the phenomena of menstruation is accompanied by 

 decided alterations in the structure of the uterine mucosa. In spite of the 

 difficulty of obtaining sufficiently fresh and well preserved material, certain 

 changes which characterize the menstruating uterus are now definitely 

 known. These chiefly consist in increased vascularity, hypertrophy of the 

 elementary tissues of the mucosa, epithelial desquamation, and rupture of 

 the blood-vessels, with consequent hemorrhages. These changes are fol- 



