38 OBSTETRICS. 



RATIONAL SIGNS. SENSIBLE SIGNS. 



4. Constant desire to evacuate the that the membranes may be felt. In 

 bladder and rectum. the primiparoe, the internal orifice is 



5. The hemorrhoids, the oedema of soft and dilated, but the external re- 

 the limbs and the varicose condition of mains partially closed. During the last 

 the veins of the inferior extremities are ten or twelve days, owing to the dilata- 

 all increased. tion of the internal orifice of the cervix 



uteri, the whole cervix becomes en- 

 larged, so as to increase the size of the 

 uterine cavity ; so that in touching, the 

 finger reaches the membranes, in the 

 primiparae, after having passed the thin 

 and even margin of the os uteri. While 

 in the multiparas, the external orifice 

 of the cervix is thick and unequal. 



DEVELOPMENT OF THE FCETUS. 



It has already been stated, that after impregnation, the ovum de- 

 velopes itself by its own plastic power, out of the materials supplied 

 it by the mother. It will be remembered that it was originally con- 

 tained within the Graafian vesicle, and that it contains a yelk 

 similar to that seen in the hen's egg, although much smaller, in the 

 centre of which is found the germinal vesicle, on whose walls is the 

 germinal spot or nucleus, from which all the various parts of the 

 new being are developed. According to some physiologists, impreg- 

 nation takes place in the ovary, and before the rupture of the Graa- 

 fian vesicle ; according to others, the Graafian vesicle is ruptured 

 first, the ovum escapes into the Fallopian tubes and meets the male 

 sperm on its way to the uterus. Afler impregnation, the germinal 

 vesicle becomes filled with cells, which are developed from the nu- 

 cleus, until the whole mass resembles a mulberry, which, from this 

 circumstance is called the gertninal or mulberry mass. From this 

 is developed the germinal membrane, by layers of cells, which pass 

 round the yelk of the ovum, so as to enclose it, the whole being still 

 contained within the yelk membrane. The germinal membrane 

 consists of three layers ; the external, which is formed first, is called 

 the serous, the middle is called the vascular, and the internal is 

 called the mucous. The external layer becomes the integument ; 

 the middle, the vascular system ; and the internal, the digestive 

 apparatus. 



The umbilical vesicle is formed by the doubling in of the mucous 

 layer under the abdomen of the foetus, so as to enclose a cavity con- 

 taining the yelk, which communicates with the digestive tract. Upon 

 this yelk the embryo subsists as long as it lasts, the umbilical vesicle 

 becoming smaller and smaller as it is absorbed, until finally only a 

 narrow orifice remains, which ultimately closes up and the umbilical 

 vesicle is thrown off; it may, however, be detected upon the umbi- 

 lical cord up to a late period of pregnancy. (Fig. 12.) 



Tlie AUafilois. — After the yelk has been entirely absorbed, it 



