52 EVOLUTION AND DISEASE. } 
different mode of working to that adopted by me, has 
come toa 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.t 
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 | 
* Those interested in this question will find the matter discussed 
in my monograph on Dermoids. Gaskell’s views are published 
in the Yournal of Physiology, April, 1889, vol. x. part 3. 4 
