CHAP, i.] TISSUES AND MECHANISMS OF DIGESTION. 433 



sorption may contribute to the first rise also, but it is more 

 probable that so marked and sudden a rise as this is carried 



2|3|4|5|6|7|8|9|lO|ll|l2|l3|l4lj5,l6l I I 2 I 3 \A-\ 5 j 6| 7\8 \ Q ||0 



FIG. 69. DIAGRAM ILLUSTRATING THE INFLUENCE OF FOOD ON THE SECEETION OF 

 PANCREATIC JUICE. (N. 0. Bernstein.) 



The abscissae represent hours after taking food ; the ordiuates represent in c.c. 

 the amount of secretion in 10 min. A marked rise is seen at B immediately after 

 food was taken, with a secondary rise between the 4th and 5th hours afterwards, 

 Where the line is dotted the observation was interrupted. On food being again 

 given at C, another rise is seen, followed in turn by a depression and a secondary 

 rise at the 5th hour. A very similar curve would represent the secretion of bile. 



out by some nervous mechanism. The details of this mechanism 

 have however not as yet been satisfactorily worked out. 



The pancreas derives its nerves, which reach it along its blood 

 vessels, from the solar plexus of the splanchnic system, but the 

 ultimate origins of the fibres have not been traced outr^lsome of 

 them however certainly come through the plexus from the right 

 vagus. 



Stimulation of the medulla oblongata, or of the spinal cord, 

 will call forth secretion in a quiescent gland, or increase a secretion 

 already going on. From this we may infer the existence of a 

 reflex mechanism, though we cannot as yet trace out satisfactorily 

 the exact path of either the afferent or the efferent impulses ; all 

 we can say is that the latter do not reach the pancreas by the 

 vagus, since stimulation of the medulla is effective after section 

 of both vagi. 



A secretion already going on may be arrested by stimulation 

 of the central end of the vagus, and the stoppage of the secretion 

 which has been observed as occurring during and after vomiting 



p. 



28 



