General Principles of Physiology . 269 



influence of the brain, or to the injury done to those surfaces by 

 the act of dividing their nerves*. That it produces its effects 

 in the former of these ways, appears from the following facts. 

 Wheij^ecreting surfaces are deprived of their nervous influence 

 by any other means, the effect is the same ; this effect is not at 

 all proportioned to the degree of injury done to the nerves, but to 

 the degree m which the nervous influence is withdrawn; and, as 

 soon as the nervous influence is restored, the surface is a4in 

 capable of its functiont. These facts seem sufficient to have^an- 

 swered the question, although it had not been determined by some 

 late experiments, in which Mr. Brodie and Mr. Cutler were so 

 good as to assist me J, that it is necessary, after the division of 

 the nerves, to displace one of the divided ends, in order wholly to 

 arrest the function of the secreting surface, the influence of 

 fbe bram still passing in such a quantity, if this be not done, as 

 to bestow on that surface a considerable degree of the secreting 

 power; and that even when the divided ends, if not otherwise 

 displaced, are separated to a distance of a quarter of an inch. 



Thus, we find, that the effect of dividing the ganglionic 

 nerves is of a nature wholly different from that of dividing the 

 cerebral, or spinal nerves; while the division of the latter only 

 deprives the animal of the power of exciting the muscles of volun- 

 tary motion, that of the former deranges the functions on which 

 Its life depends. Even the structure of the lungs, we have just 

 seen, is evidently disordered in a few hours by ihe division of 

 the eighth pair of nerves in the neck. 



As the function of the stomach is destroyed when the in- 

 fluence of the brain through the eighth pair of nerves is cut off, 

 we should at first view infer, that it is from the brain alone that 

 the stomach derives its nervous influence. But although the oro- 

 cess of digestion be suspended by the division of these nerves, it 

 does not follow that the stomach may not derive nervous in- 

 fluence from some other source, because the loss of any consi- 

 derable part of this influence may destroy its function. Besides, 



* Journal of the Royal Institutioo, No. 17, 



t lb. No. 18, page 257- 



I lb. No. 23, page 17, et seq. 



Vol. XIII. U 



