242 



PHYSIOLOGY 



CHAl'. 



pressure when the uterus has attained a certain size. Obstruction 

 to the return of venous blood from the lower limbs, which may cause 

 varicose distension, is frequently observed. In the last month 

 of gestation the increased size of the uterus exercises a mechanical 

 influence also on the thorax, limiting the inspiratory movements 

 of the diaphragm and widening its base in a transverse direction. 



Fio. 104. Tenth month : head in position in pelvis ; anterior vaginal fornix introflexed and 

 vestibule apparently destroyed. (13umm.) a, internal uterine oritice; b, external uterine 

 orifice. 



It has been frequently erroneously supposed that cardiac 

 hypertrophy was caused by pregnancy, this idea being due to 

 the fact that percussion of the cardiac region at*the end of gesta- 

 tion shows a more extended area of absolute dullness. This 

 phenomenon is due to the higher level of the diaphragm, which 

 forces the heart to assume a transverse position and incline more 

 towards the anterior wall of the thorax (Gerhardt). For the same 

 reason the apex of the heart is pushed about 2 mm. further 



