i62 HEREDITY 



combined action seems to be the most probable 

 hypothesis. One thing, however, appears certain : the 

 nerve-cells, whether they be motor or sensory, and 

 whether their fibres be afferent or efferent, vibrate 

 strictly in measure and in accordance with the 

 chemical processes which are taking place. Further, 

 the effects of this vibration are felt in other parts of 

 the nervous system besides the specially active cells, 

 so that any other cells ready or inclined to vibrate 

 would quickly do so in response to, and in accordance 

 with, the stimulus. The argument, therefore, runs 

 thus : Chemical force is liberated in the processes of 

 physiological action and tissue change. Force will 

 inevitably travel most readily along the lines of least 

 resistance or of greatest conductivity, that is to say, 

 along the nervous channels, and as it does so it will 

 stimulate most easily the most excitable centres, 

 which are the normally hypersensitive centres con- 

 trolling the generative organs. These in turn will 

 vibrate in measure and in agreement with the nature 

 of the stimuli reaching them from every part of the 

 body and due to metabolic action. In such a state- 

 ment, it will be understood, allowance must be made 

 for counteracting influences, which, however, though 

 they modify, do not essentially alter the normal 

 conditions. 



The part which the cerebellum plays in the repro- 

 ductive processes is the same as in other forms of 

 physiological action, namely that of a reinforcing 

 organ. 



