IN THE THEORY OF NATURAL SELECTION. 315 



them once or twice sharply upon the head : the epileptic attack 

 took place immediately and was afterwards repeated. It is obvious 

 that the presence of microbes can have nothing- to do with such an 

 attack, but the shock alone must have caused morphological and 

 functional changes in the centres of the pons and medulla oblongata, 

 identical with those produced by microbes in the other cases. 

 Nothnagel also distinctly expresses the opinion that epilepsy ' does 

 not depend upon one uniform and invariable histological change, 

 but that the symptoms which constitute the disease may in all pro- 

 bability be caused by various anatomical alterations, provided that 

 they take place in parts of the pons and medulla which are mor- 

 phologically and physiologically equivalent 1 .' Just as a sensory 

 nerve produces the sensation of pain under various stimuli, such as 

 pressure, inflammation, infection with the poison of malaria, etc., 

 so various stimuli might cause the nervous centres concerned to 

 develope the convulsive attack which, together with its after-effects, 

 we call epilepsy. In Westphal's case, such a stimulus would be 

 given by a powerful mechanical shock, in Brown- Sequard's experi- 

 ments, by the penetration of microbes. 



However, quite apart from the question of the validity of this 

 suggestion, w 7 e can form no conception as to the means by which 

 an acquired morphological change in certain nerve-cells a change 

 which is not anatomical, and probably not even microscopical, but 

 purely molecular in nature can be possibly transferred to the 

 germ-cells : for this ought to take place in such a manner as to 

 produce in their minute molecular structure a change which, after 

 fertilization and development into a new individual, would lead to 

 the reproduction of the same epileptogenic molecular structure of 

 the nervous elements in the grey centres of the pons and medulla 

 oblongata as was acquired by the parent. How is it possible for all 

 this to happen ? What substance could cause such a change in the 

 resulting offspring after having been transferred to the egg or sperm- 

 cell ? Perhaps Darwin's gemmules may be suggested ; but each 

 gemmule represents a cell, while here we have to do with molecules 

 or groups of molecules. We must therefore assume the existence 

 of a special gemmule for each group of molecules, and thus the 

 innumerable gemmules of Darwin's theory must be imagined as 

 increased by many millions. But if we suppose that the theory 



1 l. c., p. 269. 



