Ill 



DIGESTION IN THE MOUTH AND STOMACH 203 



the cord above the striae acusticae, but after 4-5 hours apo- 

 morphine produces vomiting of a special kind, which sets in 

 suddenly, as if an inhibitory influence had expired, so that the 



FIG. 70. Tracing of rhythmical and periodic movements obtained in the pyloric region, after 

 extirpation of caeliac plexus. (Ducceschi.) 



action of the spinal centres which are simultaneously trying to 

 induce vomiting, coine into play. In any case, it is certain that 

 the respiratory centres of the bulb are quite distinct from the 

 vomiting centres. In fact, when the conditions for vomiting fail 



Fi<;. 71. --Tracing of periodic movements in cardiac region, after extirpation of 

 caeliac plexus. (Ducceschi.) 



owing to central lesions, an excessive tachypnea can be observed. 

 As on the other hand abdominal compression, i.e. the synchronous 

 contraction of diaphragm and abdominal muscles, intervenes 

 actively in the production of vomiting, we must, in order to 

 sustain the doctrine of a special unitary centre for vomiting also 



