860 PHYSIOLOGY. 



THEORY OF MENSTRUATION. There are two theories. In 

 Pflueger's theory, the discharge of blood is looked upon as a phy- 

 siological freshening of the tissue, like in surgery, for the recep- 

 tion of the ovum and its union with the mucous membrane. 



In Reichert's theory, before the discharge of the ovum a change 

 takes place in the uterine mucous membrane, which becomes swollen 

 up, more spongy, more vascular, and more ready to nourish an 

 impregnated ovum. If the ovum is not impregnated, then there is 

 degeneration of the uterine mucous membrane, and a flow of blood 

 ensues. 



Both theories believe that menstruation is a preparation of the 

 uterine mucous membrane for the reception of the ovum. 



It is usually recognized that ovulation is arrested during preg- 

 nancy and lactation. The amount of menstrual blood is usually 

 about 4 J /2 ounces, and the flow generally lasts four days. 



Marshall and Jolly have shown that ovulation cannot be the 

 cause of either heat in animals or menstruation. They show that 

 the whole procestrous process is of the nature of a preparation for 

 the attachment of the embryo to the uterine mucous membrane. 

 The ovary of a mammal elaborates an internal secretion which, at 

 recurring periods, is the cause of the prooestrous and the cestrous. 

 The corpora lutea form a ductless gland, which is necessary for the 

 nutrition of the trophoblast during the early stages of pregnancy, 

 and subsequently atrophies. 



Bond believes the endometrium has a saline secretion peculiar 

 to the ancestrous state; that some substance is elaborated by the 

 pregnant uterus which stimulates the growth of the corpora lutea 

 in transplanted ovaries. He believes the ovary furnishes a secre- 

 tion having an anabolic influence on the uterus and produces the 

 oestrus. The saline uterine secretion is antagonistic to the action 

 of the ovarian secretion. 



Corpus Luteum. The place in the ovary where the bursting of 

 a Graafian follicle by the overdistension of the liquor folliculi ensues 

 is usually filled up with what is known as the corpus luteum. The 

 follicle collapses, and in its interior remains a lining of granulosa cells 

 and a clot of blood. Cells of the corpus luteum, containing a yellow 

 body (lutein), are formed from a proliferation of the internal con- 

 nective-tissue cells. If pregnancy ensues, the true corpus luteum is 

 larger, thicker, and deeper in color than the false corpus luteum of 

 menstruation. 



