MECHANICAL PHENOMENA. 43 



stomach, there exist in this viscus isolated ganglion cells 

 and nerve fibres from the plexus of AUERBACH and MEISSNER. 

 These local nervous elements have been looked upon as 

 causing the rhythmical contractions of the stomach, but 

 it is questionable whether the unstriped muscle fibres are 

 not themselves responsible for this. It approximates cor- 

 rectness most nearly, no doubt, when we say that the un- 

 striped muscle fibres of the stomach are capable of the 

 rhythmical and the sustained contractions which we observe 

 in this organ, but that these contractions can be markedly 

 influenced through the nervous system. 



In addition to the local nerve-cells and plexuses, and the 

 vagus and sympathetic fibres which go to the stomach, 

 there exist in the spinal cord and the ganglia at the base 

 of the brain so-called " centres " which on stimulation lead 

 to muscular contractions or relaxations in the stomach, but 

 we do not understand how these different elements cooperate 

 to bring about the ordered movements observed in this viscus 

 after an ordinary meal, or the disturbances noted in certain 

 pathological states. 



The small intestine is supplied by branches from the vagus 

 nerves and from the sympathetic system. The sympathetic 

 fibres come to the intestine in part from the solar and lum- 

 bar plexuses, in part by way of the splanchnics. Stimu- 

 lation of the vagus brings about in the small intestine as 

 in the stomach motor effects which may evidence them- 

 selves in rhythmical contractions, or in sustained tonic con- 

 tractions. The chief effect of stimulation of the sympa- 

 thetic fibres seems to be that of inhibition. As was first 

 shown by PFLUGER, stimulation of the splanchnics leads to 

 cessation of movement in the small intestine. From MALL'S l 

 careful studies it is known that an anemia of the intestines 

 causes a cessation of movement in them, and it was once 

 thought that the inhibition of movement when the spianch- 



1 MALL: Johns Hopkins Hospital Reports, 1896, 1, p. 37, 



