PREGNANCY. 31 



mother, at first by absorption through the villi of the chorion, and 

 afterwards by the placenta, and the uterus increasing in size, and 

 producing upon its interior face a membrane called the caducous, or 

 deciduous, the formation of which has been variously explained. 

 According to Dr. W. Hunter, the whole interior of the uterus becomes 

 coated with a pulpy fluid, which covers over the cervix and Fallopian 

 tubes ; this becomes hard, and resembles coagulated lymph, and is 

 called the decidua vera. As the ovum now descends the Fallopian 

 tubes on its way to the uterus, it comes in contact with this mem- 

 brane at the orifice of the Fallopian tubes, and pushes it before it, at 

 the same time that it is reflected over itself, thus forming the decidua 

 rejlexa. According to Dr. Carpenter, this is not altogether the true 

 account of it. It appears from the late researches of Dr. Sharpey 

 and Professor Weber, that the decidua is really composed of the inner 

 portion of the mucous membrane of the uterus itself, which undergoes 

 a considerable change in its character. Dr. Reid has described a tubu- 

 lar structure on the free surface of the uterus, which becomes thick- 

 ened and increased in vascularity within a short time after conception ; 

 and when the inner surface of a newly impregnated uterus is ex- 

 amined with a low magnifying power, the orifices of its tubes are 

 very distinctly seen, being lined with a white epithelium.* This is 

 perhaps the more correct view, since the decidua reflexa is found to 

 be different in its structure from that of the vera, which would not 

 be, were they formed as described by Hunter. When an ovum has 

 been thus fecundated, and brought to maturity in the uterus, before 

 extrusion, it is called viviparous generation. This is the variety 

 which occurs in the human female. 



PREGNANCY, ITS PHENOMENA AND DISEASES. 



Before entering upon the consideration of the signs by which a 

 woman knows herself to be pregnant, it will be proper to examine 

 what farther changes take place in the uterus itself. It has already 

 been stated that the uterus becomes more vascular, after conception 

 has taken place, and that its interior lining becomes altered ; the 

 vessels, arteries, veins, and lymphatics are increased in size, and it 

 has been said by Dr. Robert Lee, that the nerves are also increased 

 in numbers, although this latter change is doubted by many. The 

 proper tissue of the uterus also undergoes great changes. In propor- 

 tion as the ovum is developed, the fibres are separated from each 

 other, and increased in number, leaving spaces betw^een them which 

 are filled by the enlarging vessels (Fig. 10). That the amount of 

 substance is absolutely increased, is shown by the difl^erence of weight 

 between a virgin uterus, and one at full term, just emptied ; the former 

 Weighing one ounce, the latter nearly twenty-four. The increase in 



* Human Physiology, Am. edition, p. 201-2. 



