CH. XXXI.] NERVES OF THE STOMACH. 483 



was a reflex and abundant flow of gastric juice, which commenced 

 five minutes after the beginning of the meal. If water, milk, or 

 soup was given instead of meat no such secretion occurred. 



The same phenomena occurred when both splanchnics were 

 divided. It is therefore evident that the splanchnics are not the 

 secretory nerves. But after division of both vagi (below the point 

 of origin of the recurrent laryngcal nerves to avoid paralysis of the 

 larynx), the reflex secretion ceased, though the dog went through 

 the process of sham feeding with the same avidity as before. 



The vagi therefore contain the secretory fibres ; this conclusion 

 was confirmed by the experiment of stimulation. If the peri- 

 pheral end of a divided vagus is stimulated, however, the usual 

 result is stoppage of the heart ; this difficulty was overcome by 

 letting a few days elapse between the division of the nerves and 

 the experiment of stimulating them. During this time the cardio- 

 inhibitory fibres degenerated, and then stimulation of the nerve 

 by induction shocks at intervals of one second called forth a flow 

 of gastric juice, after a latent period of about five minutes. 



Pawlow's method enabled him to obtain a gastric juice free from any 

 admixture with saliva or food. The main facts in relation to this pure 

 juice are as follows : It is clear and colourless ; it has a specific gravity of 

 1003 to 1006. It is feebly dextro-rotatory, gives no biuret reaction, but 

 gives the ordinary proteid reactions. It contains from o'4 to o - 6 per cent, 

 of hydrochloric acid. It is strongly proteolytic and inverts cane sugar. 

 When cooled to o C. it deposits a fine precipitate of pepsin ; this settles in 

 layers, and the layers first deposited contain most of the acid, which is 

 loosely combined with and carried down by the pepsin. Pepsin is also 

 precipitable by ammonium sulphate (Kiihne). Elementary analysis gave 

 the following results : 



Pepsin precipitated by cold Precipitated by Am 2 S0 4 - 



Carbon .... 5073 per cent. 

 Hydrogen .... 7-23 

 Chlorine . . roi to 1-17 

 Sulphur .... 0*98 .. 

 Nitrogen . . . not estimated 

 Oxygen . . . the remainder. 



50-37 



6-88 



0-89 



i'34 



14-55 to 'S'o 

 the remainder. 



Since these experiments were performed, Pawlow has continued his work 

 on gastric secretion. He has by a very ingenious surgical operation suc- 

 << 'i|i-d in the d<>g in separating off from the stomach a diverticulum which 

 pours its secretion through an opening in the abdominal wall. The follow- 

 ing are his main results : 



1. Increase in the quantity of food given causes an increase in the amount 

 of gastric juice secreted. 



2. The juice is most abundant in the early periods of digestion, but 

 it continues to be secreted in declining quantity as long as any food remains 

 to be dealt with. When there is no food given there is no juice. But sham 

 feeding or chewing will cause it to flow. 



3. The amount of pepsin secreted is similarly proportional to the needs of 

 the animal. 



4. The larger the pro|M>rti<>n of proteid in the diet, the more abundant 

 and active is the juice secreted. 



I I 2 



