in DIGESTION IN THE MOUTH AND STOMACH 197 



aspirate the contents of the stomach into the oesophagus, if the 

 cardia be opened simultaneously. This mechanism is facilitated 

 by the simultaneous rise in abdominal pressure owing to the 

 contraction of the diaphragm and abdominal muscles. The 

 retching which precedes evacuation of the gastric contents is due 

 to this oesophageal aspiration. 



Lastly, in vomiting, there is an elongation of the oesophagus, 

 caused by the contraction of its longitudinal fibres, and by the 

 movements of mouth, pharynx, and larynx, as thoroughly worked 

 out by Dzondi (1831). The closure of the pharyngo-nasal cavity 

 and glottis is effected by a mechanism identical with that which 

 occurs in the act of deglutition ; but, contrary to deglutition, the 

 tongue and roof of the mouth are not raised but are lowered, 

 because in vomiting the mouth must be open. According to 

 Dzondi the mouth, which is relaxed in deglutition, must contract 

 in vomiting, to resist the passage of the contents of the stomach 

 by the choanus. 



XI. The innervation of the gastric muscles is still a very 

 obscure and imperfectly studied field. The observation of various 

 experimenters, particularly Hofmeister and Schlitz, to the effect 

 that the stomach, when excised from the body and brought into a 

 warm glass chamber, is capable, like the heart, of performing 

 spontaneous movements, shows that it possesses in itself all the 

 conditions necessary to its movements, its automatic and reflex 

 centres being probably represented by the gangliated groups in 

 Auerbach's plexus. This fact, however, does not exclude the 

 controlling and regulating influence of the cerebrospinal nervous 

 system, transmitted to the stomach by way of the vagi and 

 splanchnics. 



Longet first suggested that the vagi exercise a motor influence 

 on the stomach, which, however, in his opinion is manifested 

 only after a meal, and not on the empty stomach. S. Mayer, 

 Eusso-Giliberti, and Morat confirmed this influence of excitation. 

 Division of the vagi, on the contrary, gives very uncertain 

 results: according to some the gastric movements persist (Magendie, 

 Bidder and Schmidt, Donders, Schiff) ; according to others they 

 are suspended or at least much attenuated (Eawitsch, Milne- 

 Edwards, Joh. Miil'er, Longet). 



A fact worth noting, as deduced from physiological research 

 and anatomical control, is that the two vagi are not (as commonly 

 stated in the text-books) distributed, the right to the posterior 

 surface and the left to the anterior surface of the stomach. Both 

 in the higher mammals and in man, the two vagi course together 

 and form in the lower part of the oesophagus, with fibres common 

 to both, one trunk which runs to the anterior plexus, and a second 

 which is continuous with the posterior gastric plexus (Ducceschi, 

 Dorello). 



