452 PROGRESS OF SCIENCE IN THE CENTURY. 



organs of sense always produces different sensations ; 

 and that different stimuli acting on the same organ 

 of sense always produce the same sensation. Bunge, 

 from whom we have quoted the statement of the 

 law, calls it " the greatest achievement both of physi- 

 ology and psychology/^ " the greatest and deepest 

 truth ever thought out by the human intellect." * 

 " There is," Verworn f says, " scarcely any physio- 

 logical discovery which has a more important bear- 

 ing upon all psychology and the theory of knowl- 

 edge — although unfortunately it is not generally 

 appreciated — than the doctrine of the specific energy 

 of the nerves or organs of the special senses." The 

 doctrine implies " that the external world is not in 

 reality what it appears to us to be when perceived 

 through the spectacles of our sense-organs; and that 

 by the path of our sense-organs we cannot arrive at 

 an adequate knowledge of the world." 



We have already noted that Mliller was mistaken 

 in referring to the specific effects of stimulation to the 

 nerves, for since the work of Vulpian (1866) it has 

 been recognised that nerves are simply conducting 

 threads; the specific functions had to be shifted to 

 the cells of the nerve-centres. Moreover, Dr. Hill :j: 

 refers to the remarkable experiment by which ^^ the 

 vagus nerve, which ought to be supervising digestion 

 and the beating of the heart " can be made " to con- 

 trol blushing, dilation of the pupil, and the other ac- 

 tions which were formerly (are normally) within 

 the province of the cervical sympathetic. This up- 



♦ G. Bunge, Text-Book of Physiological and Pathological 

 Chemistry, trans. 1890, p. 12. 

 t M. Verworn, General Physiology, trans. 1899, p. 21. 

 XAn Introduction to Science, 1900, p. 125. 



