THE MECHANICS OF DIGESTION 



1017 



existing between this sympathetic ramification and central parts by 

 way of the mesenteric ganglion of the solar plexus and the vagi nerves, 

 and (c) the successive segments of the intestine are enabled to act in 

 unison, because the plexus of Meissner and Auerbach is arranged in 

 the form of successive reflex circuits which are correlated with one 

 another. 



The last contention is based upon the experimental evidence that 

 peristaltic waves may be incited almost anywhere along the intestine 

 which then progress in a downward direction through its successive seg- 

 ments. Additional light has been thrown upon this question by Mall 

 who has resected and reversed certain segments of the small intestine so 

 that their formerly lower ends became their upper. At autopsy, these 

 animals invariably exhibited a fusiform distention of the intestine above 

 the line of the upper suture and an accumulation of fecal material 

 which in many cases had resulted in necrosis, perforation, and peri- 

 tonitis. It is evident, therefore, that this in- 

 version of an intestinal loop causes the regular 

 peristalsis to cease at the upper line "of 

 sutures. Moreover, if an oval ball of wood 

 is inserted into the upper end of one of these 

 inverted segments, it is again expelled 

 through the same opening, whereas its inser- 

 tion through the lower orifice gives rise to a 

 peristaltic wave which moves it in the direc- 

 tion of the stomach. The question of 

 whether the intestinal movements of man 

 can at all be compared with those of other 

 animals, may be answered in the positive; 

 in fact, Carvallo, as well as Kiipferli 1 state 

 that they are identical. 



The Movements of the Large Intestine. 

 The function of the large intestine is so 

 widely different from that of the small intes- 

 tine that these two parts may almost be 

 considered as separate organs. In the car- 



nivora the process of digestion and absorption is practically completed at 

 the ileocecal valve, while in the herbivora these processes continue 

 in all their intensity distally to this point. The omnivora occupy an 

 intermediate position, but since the human large intestine is relatively 

 long and possesses a capacious cecal vestibule and peculiarly indented 

 colon, it more nearly resembles that of the herbivorous animals. 

 The ileocecal valve is a sphincter formed of a heavy band of muscle 

 tissue and two membranous flaps which are unequal in size and do not 

 close firmly. The fact that the contents of 'the cecum may be forced 

 back into the ileum with great ease, shows that it does not form a very 

 efficient sphincter. At the same time, it must be admitted that it 

 1 Zeitschr. fiir Rontgenkunde, xiv, 1912. 



FIG. 516. DIAGRAM TO 

 SHOW THE POSITION OF THE 

 ILEOCECAL VALVE. 



J, Ileum; C, cecum; A, 

 orifice of the proc. vermi- 

 formis; AC, ascending colon; 

 H, haustrum. 



