PARTUK1TION. 203 



uterus should contain the growing embryo for months, and then 

 be suddenly thrown into action to expel it, cannot be explained. 



What is the nature of the act of parturition ? 



It is a reflex action depending upon a centre in the lumbar spi- 

 nal cord. Whence the stimuli are derived which excite the reflex 

 is unknown, but probably from the organ itself. 



What is the character of the uterine contractions ? 



They are rhythmical in character, and may be compared to the 

 contractions of the heart-muscle. Each " pain " begins feebly, grad- 

 ually intensifies until it reaches a maximum, and then gradually 

 declines until it entirely dies away, to be succeded by another simi- 

 lar contraction and pause. This rhythmical action continues until 

 the uterine contents are expelled, and then the organ enters into a 

 condition of tonic contraction. 



