SEC. 2. MENSTRUATION. 



935. From puberty, which may be said to occur at from 

 13 to 17 years of age, to the climacteric, which may be said to 

 arrive at from 45 to 50 years of age, the exact time in each case 

 varying considerably and being apparently determined by various 

 conditions, the human female is subject monthly to a discharge from 

 the vagina known as the ' menses,' ' catamenia/ and by many other 

 terms. The discharge is the result of changes in the lining mem- 

 brane of the uterus, and these are accompanied by changes in the 

 ovary leading to the escape of an ovum from its Graaman follicle 

 into the Fallopian tube, as well as by certain general changes in 

 the body at large. A similar change in the uterus, associated 

 with a like escape of ova from the ovary, occurs in the lower 

 animals, being repeated at intervals differing in length in different 

 animals, and is usually accompanied by sexual excitement and 

 changes in the external genital organs ; the phenomena are then 

 spoken of by such names as ' heat,' ' rut,' &c. 



Leaving aside for the present the causation of the phenomena, 

 we may regard as at least a conspicuous event in menstruation the 

 escape of an ovum from its Graaffian follicle. The whole ovary at 

 this time becomes congested, the blood vessels becoming so dilated 

 and filled with blood that we may almost speak of the condition 

 as one of erection ; and the ripe follicle, whose ovum is about to 

 escape, bulges from its surface. The most projecting portion of 

 the wall of the follicle, which has previously become excessively 

 thin, is now ruptured, apparently by the mere distension of the 

 cavity, and the ovum, now lying close under the projecting surface 

 of the follicle, escapes, invested by some of the cells of the discus 

 proligerus, into the Fallopian tube. Much discussion has taken 

 place as to how the entrance of the ovum into the Fallopian tube 

 is secured. We have seen ( 924) that probably under ordinary 

 circumstances the ovary is embraced by the trumpet-shaped 

 fimbriated mouth of the Fallopian tube, and the contact is 

 probably rendered more complete by the turgid and congested 

 condition of both organs ; it is possible that the plain muscular 

 fibres present in the mouth of the tube may assist, and indeed 



