544 NERVOUS SYSTEM 



finger introduced through the fistula is firmly grasped by the contrac- 

 tions of the muscular walls. When the pneumogastrics are divided, the 

 contractions of the muscular walls cease, the mucous membrane becomes 

 pale, the secretion of gastric juice apparently is arrested and the sensi- 

 bility of the organ is abolished. 



Notwithstanding the apparent arrest of the movements of the stom- 

 ach in digestion by section of the pneumogastrics, it has been shown 

 that substances may be slowly passed to the pylorus, and that the 

 movements, although they are greatly diminished in activity, are not 

 entirely abolished. The movements occurring after section of the 

 nerves have been attributed to local irritation of the intramuscular ter- 

 minal nervous filaments. 



The influence of the pneumogastrics on the general processes of 

 digestion, the sensations of hunger and thirst and on absorption from 

 the alimentary canal have already been considered in connection with 

 the physiology of digestion and absorption. 



Influence of the Pneumogastrics on the Small Intestine. The pneu- 

 mogastrics influence intestinal as well as gastric secretion. After 

 section of the nerves in the cervical region, powerful cathartics (croton- 

 oil, calomel, podophyllin, jalap, arsenic etc.) fail to produce purgation, 

 even in doses sufficient to cause death. The articles used may be given 

 by the mouth just before dividing the nerves or may be injected under the 

 skin. 



Stimulation of the pneumogastrics excites peristaltic movements of 

 the small intestine. Experiments on the lower animals have shown, 

 however, that if the nerve is stimulated during peristalsis, the move- 

 ments are inhibited for a few moments, but afterward are increased in 

 activity. 



The cranial nerves that have been considered are the third, fourth, 

 fifth, sixth, seventh, tenth, eleventh and twelfth. The anatomical and 

 physiological history of the olfactory (first), optic (second), auditory 

 (eighth), gustatory (branch of the seventh and a part of the ninth) and 

 of the general sensory nerves so far as they are concerned in the sense 

 of touch, belongs properly to the chapters on the special senses. 



