INVOLUTION OF THE UTERUS 85 



uterus contracts but little and slowly. Then the lochia are not 

 evacuated, but accumulate in the uterus. This state is termed 

 inertia uteri, or uterine sluggishness. Severe hemorrhages, as 

 in man, do not happen in this state. Since the cervix uteri 

 remains open on account of the wanting uterine contractions, a 

 factor quite favorable to the chemical change of the liquid is 

 present. 



The weight of the uterus always decreases during the 

 process of involution. Baumeister and Rueff state that the 

 uterus of a medium sized cow immediately after parturition 

 weighs 6 to 7 kg., later 500 to 600 g. All three layers of the 

 uterus lose in weight, especially the muscularis and mucosa. 

 Let us now consider some points a little closer : First, the 

 puerperal involution of the uterine muscle. Since the middle 

 of this century examinations in regard to the involution of the 

 uterine muscles have been made. Kilian mentions as the 

 predominating theory of his time, that the muscular fibres are 

 compressed by the after pains, and that the liquid thus squeezed 

 out is partly removed by the lochia and partly resorbed. 



According to Kolliker, the process of involution in the 

 beginning of gestation depends on hypertrophy and hyperplasia 

 of the muscles, but after the fifth month of pregnancy hyper- 

 trophy only persists ; he says : " After parturition the fibrillar 

 cells of the gravid uterus rapidly decrease in length, at least I 

 found them three weeks after delivery only about .03 mm. long, 

 and filled with many larger and smaller fat drops arranged in 

 rows." 



Kilian experimented a good deal with rabbits and guinea- 

 pigs. He found that all the old fibres perish and become 

 replaced by newly formed cells. One might therefore rather 

 speak of a regeneration or restitution than involution. 



Heschl agrees with Kilian on the main points, but he thinks 

 that the development of fibres only begins in the fourth week 

 of the puerperal state. After two months he found the whole 

 uterus regenerated. He is further of the opinion that puerperal 

 processes, chronic diseases and anomalies in the shape of the 

 uterus, have none or but little influence upon its involution, 



