314 THE CAUSATION OF DISEASE. 



is indeed the truth. So far as I know, all the purely functional 

 diseases included in Class b originate in such a lesion of the 

 nerve centres, for these structures have under their immediate 

 control the entire working of the body. If an organ presents 

 no obvious lesion, we may safely reckon upon its healthy 

 action, provided its nervous apparatus be efficient. On the 

 other hand, an undiscoverable lesion of this or that nerve- 

 centre may profoundly modify the E of any cell in the body, 

 and may give rise to symptoms referable to any organ which it 

 governs, be it heart, lungs, stomach, muscle, or any other. 



