vi PREGNANCY PARTUPJTIONPUERPERIUM 237 



pregnancy the fibres may attain a length of 500/*, that is, may 

 become ten times longer than those of the virgin uterus, as is 

 shown in Fig. 100. 



The development of the blood-vessels proceeds at the same 

 rate as that of the muscular system. In order to form an adequate 

 idea of this it is only necessary to examine the figure of the 

 pregnant uterus with the arteries and veins injected in a pre- 

 paration by Hyrtl. In looking at it we are surprised at the 

 turgescence, the dilatation, the numerical increase, the winding 

 course and the multiple anastomoses of the veins which cross 

 the muscular fibres in every direction. While the largest uterine 

 and internal spermatic arteries are scarcely as thick as a crow 



a 



B 



FIG. 99. Transverse sections of the umbilical cord, according to Minot. A, embryo 21 mm. in 

 length ; B, foetus aged sixty-four to sixty-nine days, oa, umbilical arteries ; r, umbilical 

 vein ; all, allantoid duct ; c, coelom ; o, peduncle of umbilical vesicle, accompanied by omphalo- 

 mesenteric vessels. 



quill, the largest venous trunks of the same name are as thick 

 as the little finger (Fig. 101). The lymphatic vessels also increase 

 notably in both number and size ; they are invisible in Hyrtl's 

 diagram, because they had not been injected. Gynaecologists 

 have also described a hypertrophy and hyperplasia of the nerves 

 and ganglia, which are related to the genital region and cover 

 the wall of the uterus and its connections. On the other hand, 

 the connective tissue surrounding the muscular fibres, vessels, 

 and nerves shows during pregnancy a progressive tendency to 

 softening and absorption of fluid, causing the component parts 

 of the uterine wall to separate more easily and the organ to 

 distend more readily, as is required by the increase in size of the 

 ovum (Fig. 102). 



The increase in thickness of the uterine wall reaches its 

 maximum about the end of the third month ; during the following 



