PXEUMOGASTEIC NERVES. 213 



in the cervical region in living animals have noted their ex- 

 ceedingly dull sensibility, as compared with the ordinary 

 sensory nerves. Bernard, indeed, states that in this region 

 they are generally insensible ; 1 but we have usually found, 

 in dogs at least, that their division is attended with slight 

 evidences of pain. Without citing in detail all the experi- 

 ments on this point, it is sufficient to state that some physi- 

 ologists, on galvanizing or otherwise irritating the roots of 

 the nerves in animals just killed, have noted movements of 

 the muscles of deglutition, of the oesophagus, and the muscu- 

 lar coats of the stomach. These experiments have led to the 

 opinion that the proper roots of the nerves are motor as well 

 as sensory. It becomes, therefore, a difficult as well as an 

 important point to determine whether or not the roots be 

 of themselves exclusively sensory or mixed. 



In discussing the properties of the roots, we shall rely 

 almost entirely upon direct experiments ; though the argu- 

 ments drawn from their anatomical characters, in the pres- 

 ence of ganglia and the deep origin of their fibres, point 

 strongly to their sensory character. 



It is impossible to stimulate the roots, before they haA^e 

 received motor filaments from other nerves, in living ani- 

 mals, and the experiments are therefore made upon animals 

 just killed, before the nervous irritability has disappeared. 

 If the true roots of the nerves be exclusively sensory, their 

 galvanization in animals just killed should produce, by di- 

 rect action, no muscular contraction. If the roots contain 

 any motor filaments, contraction of muscles should follow 

 their stimulation. The proper physiological conditions in 

 such experiments are the following : 



1. It is necessary to stimulate the roots so that the fila- 

 ments from the spinal accessory and other motor nerves be 

 not involved. 



2. It is important to ascertain, provided movements follow 

 such irritation, whether or not they be due to reflex action. 



1 BERNARD, Systeme nerveux, Paris, 1858, tome ii., p. 345. 



