404 GENERATION. 



later than the parts connected with vision and audition. The 

 vesicles themselves become filled with ganglionic matter, and 

 constitute the olfactory bulbs, their pedicles being the so- 

 called olfactory nerves, or commissures. 



As far as the functions of the nervous system of the 

 foetus are concerned, it is probable that they are mainly re- 

 stricted to reflex phenomena depending upon the action of 

 the spinal cord, and that perception and volition hardly 

 exist. It is probable that many reflex movements take 

 place in utero. When a foetus is removed from the uterus of 

 an animal, even during the early periods of pregnancy, move- 

 ments of respiration occur, a fact which we have often de- 

 monstrated to medical classes ; and it is well known that ef- 

 forts of respiration sometimes occur within the uterus. This 

 we believe to be a reflex action excited by the want of oxy- 

 gen in the tissues, when the placental circulation is inter- 

 rupted. We have already discussed these phenomena in an- 

 other volume. 1 



1 See vol. i., Respiration, p. 487. 



