5 2 E VOL UTION AND DISEASE. 



different mode of working to that adopted by me, has 

 come to a similar conclusion. Gaskell's conclusions are 

 based mainly on the fact that the central nervous system 

 is composed of two parts, a nervous and a non-nervous 

 element, especially in the cranial region, and he considers 

 that the nervous elements have been thrust upon and 

 thus utilized the alimentary tube as a supporting struc- 

 ture. Gaskell has entered minutely into details con- 

 cerning the modification induced by the change in the 

 position of the mouth. 



Which of the views is the correct one whether the 

 gut, becoming disused from gradual loss of function, 

 became utilized for the support and extension of the 

 surrounding nerve ganglia, or was rendered useless in 

 consequence of the encroachment of nervous material, 

 or, what seems equally probable, the change of its intrinsic 

 elements into nerve-cells, will require further investiga- 

 tion. 1 



Apart from such considerations, the view that the 

 central nervous system is disposed around a modified 

 piece of intestine, offers an explanation of several 

 otherwise inexplicable phenomena which will be duly 

 considered in some of the ensuing chapters. 



Tails. Among suppressed parts, so far as man is 

 concerned, must be included the tail. That man has 

 descended from forms furnished with tails cannot be 

 doubted, for at the end of the vertebral column he still 

 carries three, four, and occasionally five rudimentary 



1 Those interested in this question will find the matter discussed 

 in my monograph on Dermoids. Gaskell's views are published 

 in the Journal of Physiology, April, 1889, vol, x. part 3. 



