10 BO\INE OBSTETRICS 



According to Kilian, the increase of volume during preg- 

 nane)' depends on an increase in numbers and size of the 

 muscular elements. Kolliker traces the evolution of the 

 uterine muscle in the beginning of gravidity both to hyper- 

 plasia and hypertrophy. According to him, the former only 

 is of importance after the fifth month. Already at the end of 

 the sixth month he found muscle cells of T V to ^ mm. in 

 length, in all the layers of the muscularis. 



Eeichman measured numerous muscle cells of the gravid 

 uterus at various stages in the physiological laboratory of the 

 Utrecht Veterinary School. For this purpose he took small 

 pieces of the uterine wall of slaughtered pregnant animals and 

 removed the mucosa and serosa. The further pregnancy had 

 advanced the easier was the isolation of the uterine muscle, — 

 in all probability due to an increase of loose connective tissue 

 between the layers. The muscle was cut into little pieces of 

 7 mill, and macerated in 30 percentic nitric acid ; 48 hours 

 later rinsed in distilled water, the water renewed and the little 

 pieces shaken in it. This isolated the muscle cells the easier 

 the further pregnancy had progressed. The muscle cells of 

 the empty uterus appear spindle shaped, somewhat swollen in 

 the middle while the ends are pointed, the nucleus is long. 

 Cells with several nuclei were not observed ; after the twenty- 

 first week smaller muscular elements became also noticeable. 

 The measurements proved that as pregnancy advances the 

 muscle cells increase more in length than in width. Up to the 

 twenty-first week both length and thickness increased; after 

 that period the diameter remained stationary. Therefore the 

 increase in size of the uterine muscle up to the fifth month 

 must be attributed to hypertrophy ; later, new muscle cells 

 appear, and then only hyperplasia can be spoken of. The 

 mucosa undergoes the most important changes, especially 

 where the fecundated ovum develops. A new organ is formed, 

 or rather a number of new formations arise, the placentae 

 maternse. These growths, all built alike and forming together 

 the placenta, regress after parturition, and the mucous mem- 

 brane of the uterus returns to its original state. 



