RECENT ADVANCES IN SCIENCE. 353 



recognized that the due regulation of many of, if not all, the so-called 

 nervous centers was secured not merely by the intrinsic forces of pas- 

 sive rest making themselves felt in the absence of stimulation, but also, 

 and even more so, by the alternating play of antagonistic influences. 

 Throughout all the sciences the resolving a stability seemingly due to 

 intrinsic causes into an equilibrium arising out of the balance of oppos- 

 ing forces has again and again marked a step forward; and it is per- 

 haps not too much to say that a like analysis, prompted by the story 

 of the vagus and the heart, has profoundly modified all our conceptions 

 of the way in which nervous impulses, sweeping along the intricate yet 

 ordered network of paths in the brain and spinal cord, determine the 

 conduct of life. The idea has of course been abused as well as used, as 

 what idea has not? Such a word as inhibition could not but fail to 

 have a blessed sound in the ears of the ignorant; the idea has been 

 ignorantly and wrongly applied; but this is of little moment in view of 

 the help which it has given to wise and well-directed inquiry. 



And the idea has spread with fruitful results beyond the limits of 

 nervous impulses; it has been carried deep down into the very inner- 

 most molecular processes of life. The closer we penetrate into the phys- 

 ical-chemical events through which living matter grows, lives, and dies, 

 the clearer does it seem that life itself is a shifting outcome of two 

 opposing sets of changes — one synthetic, constructive, the other destruc- 

 tive, analytic — and that the key to this and that riddle of vital action 

 lies within the grasp of him who can clearly lay hold of the mutual 

 relations of these conflicting changes. The story of the vagus and the 

 heart is a tale, not of the heart alone, not of the nervous system alone, 

 but of all living matter. The light which first shone in the experiment 

 of the brothers Weber may, in a sense, be said to have gone out into 

 all the lands of physiology. 



Let me now turn your attention to an experiment made a few years 

 later. This is also an experiment made on a living animal, and what- 

 ever good may have come out of that to which it has given rise must 

 be reckoned as the fruit of an experiment. 



In 1851 Claude Bernard made known that division of the cervical 

 sympathetic led to a widening of the blood vessels and a warming of 

 the ear and other parts of the head and neck. This was the beginning 

 of what may rightly be called the great vaso-motor knowledge. It may 

 be true that more than a hundred years before, in 1727, Du Petit had 

 observed much the same thing, but nothing came out of it; the germinal 

 time had not yet arrived. It may be true that other observers since 

 Du Petit had divided the cervical sympathetic and noted the effects; 

 but these had their attention directed chiefly to changes in the pupil. 

 It may be true that Brown-Sequard and Waller a few months before 

 Bernard himself was able to do so supplied the complement to the origi- 

 nal experiment by showing that stimulation of the peripheral part of 

 the divided sympathetic constricted the blood vessels and reduced the 

 sm 96 23 



