A TA VI SM OR RE VERSION. 147 



neighbourhood of the contracted portion. During its 

 development the human stomach never presents itself 

 otherwise than as a single-chambered viscus. This is 

 in itself an important fact, for if in the embryo the 

 stomach presented a median contracted portion it could 

 easily be conceived that in some cases the contraction 

 would persist. It must also be borne in mind that 

 the ruminant's stomach is highly specialized ; there- 



FIG. 81. A Human Stomach with hour-glass contraction. 



fore, as reversion consists in the reappearance of a lost 

 character we shall have to show that mammals closely 

 allied to man possess such a stomach : this is not the 

 case. Thus embryology and comparative anatomy are 

 eloquent in denying the reversionary nature of hour- 

 glass contraction of the human stomach. 



Having attempted to indicate the general grounds 

 upon which suspected atavistic phenomena, in so far 

 as malformations are concerned, should be analyzed, 

 it will perhaps be interesting to discuss reversionary 

 phenomena as they manifest themselves in relation 

 with a particular organ or group of organs ; it will in 

 this way be possible to display, in a striking manner, 

 the large amount of misconception which prevails in 

 regard to atavism in general. This will serve to show 

 that reversion of organs or tissues, and the assumption 

 of function by suppressed parts, is not so frequent as 



