ATAVISM OR REVERSION. 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- 
Fic. 8r.—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 
