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EMBRYOLOGY 



pregnancy, and it is not very uncommon for the menses to appear during 

 lactation. 



When a cow gives birth to twins, one a male and the other apparently 

 a female, the latter is called a free-martin and has no ovaries. John 

 Hunter, in his paper on the free-martin, gave a full description of this 

 anomalous animal and stated that it does not breed or show any inclina- 

 tion for the bull. In an examination of a free-martin, raised and killed 

 by the late Professor James R. Wood, in 1868, the uterus was found rudi- 

 mentary and there were no ovaries (Flint). 



A menstrual period presents three stages : first, invasion ; second, a 

 sanguineous discharge ; third, cessation. 



The stage of invasion is variable in different females. There is 

 usually, anterior to the establishment of the flow, more or less of a feeling 

 of general malaise arid a sense of fulness and weight in the pelvic organs, 

 accompanied with an increase in the quantity of vaginal mucus, which be- 

 comes brownish or rusty in color and has a peculiar odor. At this time, 

 also, the breasts become slightly enlarged. This stage may continue for 

 one or two days, although in many instances the first evidence of the 

 access of a period is a discharge of blood. 



When the symptoms above indicated occur, the general sense of un- 

 easiness usually is relieved by the discharge of blood. During this, the 

 second stage, blood flows from the vagina in variable quantity, and the 

 discharge continues for three to five days. In regard to the duration of 

 the flow, there are great variations in different individuals. Some women 

 have a flow of blood for one or two days only ; while in others the flow 

 continues for five to eight days, within the limits of health. A fair aver- 

 age, perhaps, is four days. It is difficult to arrive at even an approxi- 

 mation of the total quantity of the menstrual flow ; but it has been 

 estimated at five to six ounces (150 to 175 grams). 



Supposing the menstrual discharge to continue for four days, on the 

 first day the quantity is comparatively small ; on the second and third 

 the flow is at its height ; and the quantity is diminished on the fourth 

 day. During this, the second stage, the flow has the appearance of pure 

 arterial blood, not coagulated, and mixed with epithelium from the vagina, 

 cylindrical cells from the uterus, leucocytes and a certain quantity of 

 sero-mucous secretion. Chemical examinations of the liquid have not 

 shown any marked peculiarities, except that the quantity of fibrin is 

 either not estimated or is given as much less than in ordinary blood. 



The mechanism of the hemorrhage probably is the same as in epis- 

 taxis. There is a rupture of small bloodvessels, probably capillaries, and 

 blood is thus exuded from the entire surface of the membrane lining the 

 uterus, and sometimes, but rarely, from the membrane of the Fallopian 



