190 ALBEKT KUNTZ 



quite normal control of the digestive functions in the presence of 

 vagus influences, these functions are carried on more nearly nor- 

 mally with both the splanchnics and the vagi severed than with 

 the splanchnics alone intact. These facts seem to indicate the 

 fundamental importance of the vagi in the extrinsic nervous con- 

 trol of the digestive organs. This is suggested, also, by the facts 

 of evolution. The writer has presented evidence in an earlier 

 paper ('11) in support of the theory that the peripheral sympa- 

 thetic plexuses which are genetically related to the vagi represent 

 those parts of the sympathetic nervous system which arose earli- 

 est in the process of evolution and that the vagi constitute the 

 primary connection between these plexuses and the cerebro-spinal 

 nervous system. We should expect, therefore, that the vagi 

 constitute also the primary functional connection between the 

 nervous mechanism in the walls of the internal organs and the 

 cerebro-spinal nen^ous system. 



The normal nervous control of the digestive organs is, doubtless, 

 exercised more or less directly by the local sympathetic mechan- 

 ism, the general control which is normally exercised by extrinsic 

 nerves being largely tonic in character. Inasmuch as the vagi 

 form the primary connection between the cerebro-spinal nervous 

 system and the sympathetic plexuses in the walls of the digestive 

 organs, it is highly probable that the major part of such tonic 

 control is exercised by the vagi. 



SUMMARY 



1. The ganglia of the myenteric plexus are interposed between 

 the longitudinal and the circular muscle-layers of the digestive 

 tube. The ganglia of the submucous plexus are imbedded in the 

 submucous layer. The ganglia of each of these plexuses are vari- 

 ously connected by commissures of non-medullated fibers among 

 which may be traced both axones and dendrites. 



2. The myentric and the submucous plexuses are connected 

 with each other by fibrous commissures. Nerve-fibers also extend 

 from the submucous plexus into proximity with the digestive 

 glands where many of them terminate on gland-cells and into the 



