vi PREGNANCY PARTURITION PUERPERIUM 253 



which are afterwards reabsorbed, and the fibres gradually become 

 smaller and in about four weeks reach their original dimensions 

 (Fig. 110). Just as the hypertrophy of the muscular elements 

 enlarges the bulk of the uterus during pregnancy, so the atrophy 

 restores it to its pristine size. The atrophied muscular fibres do 

 not, however, perish and give place to new ones ; according to 

 Sa'nger and other authorities, the nucleus and a portion of the 

 protoplasm of each fibre lives on 

 and undergoes hypertrophy again 

 in subsequent pregnancies. 



It is more difficult to deter- 

 mine histologically the changes 

 which take place after parturi- 

 tion in the uterine arteries and 

 veins, which during pregnancy 

 as we have already seen are 

 enormously developed, since they 

 have to supply the blood which 

 is necessary for the nutrition and 

 respiration of the embryo, the 

 foetus and the foetal adjuncts. 



The haemorrhage which follows 

 the expulsion of the foetus and 

 its adjuncts is normally slight, 

 owing to the early and energetic 

 contraction of all the muscles of 

 the uterus, including the circular 

 fibres, which are well developed 

 in the small arteries. This im- 

 mediate haemostasis becomes per- 

 manent and definitive, because the 

 venous vessels are blocked by the 

 formation of thrombi, which later 

 become organised, and the arterial 

 vessels according to Balin (1880) 

 are reduced in diameter and ob- 

 literated by the development of 

 connective tissue in the intima, with total or partial fatty 

 degeneration of the muscular portion of the tunica media. Reiss 

 (1892) found the vessels of the puerperal uterus of woman for 

 the most part occluded and considerably reduced in diameter. 

 Braers (1895) accounted for this complete or partial oblitera- 

 tion of the uterine vessels by a proliferation of the intima. 



More precise histological researches into the changes undergone 

 by the uterine vessels after parturition, compared with those which 

 take place during pregnancy, have so far only been carried out 

 on animals, white mice, and guinea pigs. The first works on the 



Fio. 110. Smooth muscular fibres of the 

 uterus in process of fatty degeneration. 

 (Bumin.) Sixth, tenth, and eighteenth 

 . day of puerperium. 



