IV 



DIGESTION IN THE INTESTINE 



245 



this passage. The beginning of the tracings (left) shows the 

 rhythmic synchronous contractions of the longitudinal and 

 circular muscle-fibres. At A a bolus made of cotton-wool coated 

 with vaseline was inserted by an opening into the intestine 

 4| inches above the enterographs. The contractions of the 

 circular coat cease instantly, and this inhibition is accompanied 

 by a gradually increasing relaxation. There is some relaxation 

 of the longitudinal coat, but the rhythmic contractions do not 

 altogether cease. At B the bolus had arrived at the upper 

 longitudinal lever, and at C had passed this, and was directly 

 under the transverse enterograph or a little below it. At this point 

 a strong tonic contraction of both coats occurs, expelling the bolus 

 beyond the levers. This strong contraction passes off, to be 



FIG. 82. Passage of a bolus down the intestine, as recorded synchronously by two enterographs 

 at right angles. Longitudinal (L), circular (C), coats. (Bayliss and Starling.) (Explanation 

 of letters in text.) 



succeeded by another, which like the first is moving down the 

 intestine. In this second tonic wave the rhythmic contractions 

 are evident, superposed on the curve. After the passage of the 

 bolus there is shortening of the gut (increased tone of longitudinal 

 fibres), and the rhythmic contractions of each coat are no longer 

 synchronous. 



Other valuable work has recently been carried out upon 

 isolated loops of intestine. Salvioli (1882) had described and 

 successfully applied an admirable technique for studying the 

 functions of parts of the intestine isolated from the animal. He 

 succeeded in nourishing these loops by artificial circulation of 

 blood serum through the superior mesenteric artery. The in- 

 testinal movements were recorded by very light levers placed in 

 different positions on the loop, so as to transmit the contractions 

 of both longitudinal and circular muscle-fibres. 



This method, with slight modifications of detail, was revived 

 in 1899 by 0. Cohnheim, and in 1904 Magnus carried out a 



