146 EVOLUTION AND DISEASE. 



similarly affected. Jn such cases as this it is easy to 

 argue that such conditions are reversions to the webbed 

 feet and hands of aquatic mammals, but careful con- 

 sideration leads me to take an opposite view. If all 

 the fingers and toes were furnished with a web we 

 should be justified in regarding the phenomenon as 

 atavistic, for in their early stages our fingers are com- 

 pletely webbed, but later the digits grow at a greater 

 rate than the web, until the skin-fold reaches no lower 

 than the middle of the first phalanx. This would lead 

 me to regard the abnormal union of fingers and toes by 

 skin-folds as a sport or spontaneous variation, and not 

 atavistic ; and this opinion is strengthened by the cir- 

 cumstance that, as we have just seen, a patagium may 

 form between the thigh and leg, a situation where such 

 a web cannot by any possible means be classed among 

 atavistic phenomena. 



In order to show to what absurd conclusions loose 

 modes of reasonings lead, reference may be made to 

 the abnormality of the stomach known as congenital 

 or hour-glass contraction. In such cases the human 

 stomach is divided by a constricted or narrow portion 

 into two compartments (fig. 81), and this has induced 

 a few observers to regard this as a reversion to the 

 complex stomach of the ruminant, especially the two- 

 chambered stomach characteristic of the genus Cervulus. 



There is, however, the following difficulty in accepting 

 this explanation. All such deformed stomachs have 

 been observed in adults ; no one has ever found a 

 double-chambered stomach in a child. Again, in many 

 of the specimens evidence of disease, such as ulcers, 

 old and recent, or scars have been detected in the 



