

NERVOUS SYSTEM UPON SECRETION 171 



Langley, alternate stimulation of the two nerves causes an increase 

 in the amount of saliva which would arise from stimulation of the 

 sympathetic only, and indicates that in normal secretion there 

 is a conjoint action of the two efferent nerves, giving rise to the 

 usual secretion. Hence we must regard the chorda tympani as 

 largely responsible for the flow of water and saline constituents, 

 and the sympathetic as responsible for the stimulation of the gland 

 cells to the production of the organic constituents and ferment. 



The Innervation of the Gastric Glands. The gastric glands, like 

 all the other digestive glands, are supplied by two sets of nerve- 

 fibres, one cerebro-spinal and the other sympathetic. In the 

 case of the stomach the cerebro-spinal fibres are supplied by the 

 vagus and the sympathetic fibres are derived from the solar plexus. 



The proof that these fibres possess an effect upon the process 

 of secretion by the gastric glands has, however, been exceedingly 

 difficult to obtain unequivocally by experiment, mainly on account 

 of the important nerve supplies to other organs and regions which 

 accompany the gastric nerve -fib res in the vagus. As a result 

 of this, section or stimulation of the vagus gives rise to profound 

 effects other than those upon the secreting cells of the gastric 

 mucous membrane, which obscure and mask, or interfere with, 

 the effects upon secretion, and hence it was only by ingenious 

 methods of avoiding such results that Pawlow and his co-workers 

 were able to demonstrate that the vagus contained excitatory 

 fibres for the secreting cells. Several of the earlier workers upon 

 the subject found that section of both vagi in the neck led to 

 suppression of the gastric secretion ; but this double operation 

 performed at one time leads to such profound disturbances that, 

 as Pawlow points out, it had little effect in encouraging a belief 

 in a causal connection between the vagus- fibres and gastric secre- 

 tion, since it is not to be wondered at that an operation which in 

 a short time brings the whole functions of the organism to a stand- 

 still should amongst other things disturb the action of the gastric 

 glands. An attitude of caution towards the results of an experi- 

 ment with such drastic consequence was suggested by the further 

 experiment of Schiff, of dividing the vagi beneath the diaphragm 

 in dogs, when, especially in young animals, there was good recovery 

 and the animals lived in excellent health after the operation. Also 

 Rutherford found that gastric secretion could be formed after 

 section of both vagi, or of both splanchnics. Similarly Pawlow 



