ELEMENTAKY DEMONSTRATIONS 



151 



CHAPTER XLII. 

 THE MOVEMENTS OF THE ALIMENTARY CANAL. 



The Movements and Innervation of the Frog's Stomach. In a 

 freshly caught frog pith the brain and cord, open the abdomen and 

 remove the sternum. Tie the pylorus and open the oesophagus, and 

 by gently compressing the stomach empty it of its contents. Then 

 tie in a tube connected by a j_-piece with (1) a recording tambour, and 

 (2) a tube containing salt solution at a pressure of 10-20 cms." 



The spontaneous movements of the stomach are localised rings of 

 contraction. These movements are not paralysed by painting the 

 outside of the stomach with -3 per cent, 

 nicotine or with cocaine. They are therefore 

 myogenic contractions. 



Pull the viscera over to the left side, and 

 remove the liver, ovary, and oviducts. Incise 

 the peritoneum and expose the rami com- 

 municantes of the spinal nerves. Place the 

 electrodes under the 4th ramus and tetanise 

 it. After a latent period of some seconds 

 the tonus of the stomach is increased. The 

 increase lasts 5 or 6 minutes. The vagus on 

 excitation inhibits the tonus and augments 

 the spontaneous movements. (Dixon.) 



DEMONSTRATION. The Movements of the 

 Cat's Stomach and Intestines. A tame 

 cat is given a meal of tinned salmon to 

 which 25 per cent, of bismuth subnitrate 

 has been added. The bowels of the animal 

 should previously have been emptied by the 

 administration of three teaspoonfuls of castor 

 oil. The cat is gently placed on its back 

 above the Rontgen light. The animal must 

 not be frightened. The movements of the 

 stomach and intestines during the digestion 

 of the meal can now be observed on a fluor- 

 escent screen (Canon). The movements of the 

 stomach begin a few minutes after the meal. seen in ^ the intestine ' (Canon ' ) 

 They consist of constrictions which appear in the middle of the stomach 

 and run towards the pylorus. Each wave takes about 30 sec. to 



Fro. 133. Contractions of the 

 cat's stomach, as seen by the 

 Rontgen ray method, after a meal 

 containing bismuth subnitrate. 

 Similar bead-like contractions are 



