GENERATION AND DEVELOPMENT 



723 



crooked — viz., the head inclining towards one side, and the hind ex- 

 tremities towards the other ; in all other respects it resembles the[mare. 

 The alteration in the position of the foetus does not occur through 



Fig. 254. — The Position occupied by the Equine Fcetus during Intra- 

 uterine Life (France). 



its own movements, but by the contraction of the uterus ; on the 

 other hand, the stretching of the limbs is the result of fcetal move- 

 ment.* "There'can be little doubt that the revolution of the foetus 



Fig. 255. — The First Stage in the Revolution of the Fcetus ; Lateral 

 Position. The Os is dilated by the Membranes which have not yet 

 ruptured (France). 



a, The Allan tois ; b, the Amnion. 



prior to birth is the explanation of the complete torsion of the neck 

 of the uterus and vagina which is sometimes found in both the 

 cow and mare. 



The dilatation of the os is assisted by the amniotic and allantoic 



* This description of the change in the position of the foetus preparatory 

 to birth is taken from Ellenberger's ' Physiologie ' (after Franck) . 



