STOMACH AND INTESTINE. 



345 



tion of the unstriped muscular coat of its in- 

 testine : a contraction which was apparently 

 excited by the air, but was certainly indepen- 

 dent of the nervous centres. This remained 

 for a time, and then disappeared, never to 

 return. Hence it seemed, in short, " a kind 

 of precipitate rigor mortis, hastened by expo- 

 sure to the air."* 



The truth of this analogy between the un- 

 striped and the striped muscle is confirmed by 

 observations made on corpses in which all ex- 

 posure of the intestine has been avoided until 

 an hour or two after death. A comparison 

 of such examinations would show that the 

 death of the intestine, like that of the ar- 

 teries, is accompanied by the access of a 

 definite rigor mortis, which is closely analogous 

 to the stiffening seen in the voluntary muscles. 

 Both the access and disappearance of this 

 contraction are, however, more rapid than 

 in the striped fibres of the proper organs of 

 locomotion. And its appearances are much 

 less distinct. In the intestinal canal, it is 

 chiefly recognized as a narrowing of the tube; 

 which is attended by an increased thickness of 

 its walls. But it is sometimes better evi- 

 denced by intus-susception of the canal; or 

 by irregular contractions of its calibre. 



But whatever the exact relation which the 

 various contractions producible in the intes- 

 tine bear to the specific structure that forms its 

 muscular wall, it seems certain that the true 

 propulsive peristalsis of the healthy living ani- 

 mal is a complex and co-ordinate act, which is 

 at least indirectly dependent upon thecerebro- 

 spinal centre. And Weber's experiments on 

 the highly excitable intestine of the Tench 

 point definitely to the medulla oblongata, as 

 that segment of the nervous centre by which 

 this connection is chiefly brought about. 

 While, as might have been expected, numerous 

 observations concur to represent the pneumo- 

 gastric and splanchnic nerves as the channels 

 by which this central organ influences the 

 alimentary canal. But the exact degree in 

 which the various vertebral and prever- 

 tebral centres of the sympathetic can trans- 

 mit, modify, or originate the nervous changes 

 which pass to and from the bowel, is at 

 present utterly unknown. There are how- 

 ever various reasons for suspecting, that 

 neither of the two main ganglia which inter- 

 vene between any part of the intestinal sur- 

 face and the cerebro-spinal centre, really limit 

 the transmission of an afferent, or give origin 

 to an efferent, change. 



Anti-peiistalsis. The ordinary theory of 

 intestinal anti-peristalsis may be 'thus stated. 

 At a certain stage of an intestinal obstruc- 

 tion, the immoderate irritation which it implies 

 reverses the natural peristalsis of the bowel ; 

 so that, instead of proceeding towards the 

 anus, it passes in the contrary direction. In 

 this way it impels the contents of the tube 

 towards the stomach ; whence they are vo- 

 mited by the aid of an extension or reproduc- 

 tion of the same action. 



About eight years ago, the author { was led 



* Author, op. cit. f Op. cit. 



to investigate this doctrine, until then uni- 

 versally accepted. He was thus led to the 

 conviction, that it ought to be uncondition- 

 ally rejected ; that it was probably false ; and 

 certainly had never been proved to be true. 

 The following were his chief reasons for 

 coming to such a conclusion : 



1. It is difficult even to conjecture any- 

 thing in the degree or kind of irritation pre- 

 sent in intestinal obstruction, which should 

 limit the occurrence of anti-peristalsis to this 

 state. 2. Since the physical state of occlu- 

 sion is the necessary condition of faecal 

 vomiting, it is probable that the causa- 

 tive process by which this occurrence is 

 brought about must be physical also. 3. No 

 anti-peristalsis has ever been observed ; the 

 movements which occur in the obstructed 

 bowel after death being similar in their nature to 

 those witnessed in the healthy intestine under 

 similar circumstances. 4. The whole of the 

 appearances seen after death in the obstructed 

 bowel, show that its contents have been pro- 

 pelled forwards towards the occlusion, and not 

 backwards from it. 5. Distention of almost all 

 the interval between the pylorus and the 

 occluded part appears to be a condition of 

 faecal vomiting ; so much so, that the date of 

 access of this symptom roughly indicates the 

 locality of the obstruction. 



Hence, instead of an imaginary anti-peri- 

 stalsis, the author ventured to propose a theory 

 which seemed to deduce the process of faecal 

 vomiting from the ascertained conditions of 

 its occurrence. 



The complete obstruction of the intestinal 

 tube at any point, gives rise to an accumu- 

 lation of its contents above the seat of the 

 structure. This gradual distention of the 

 bowel is accompanied by an active propulsion, 

 which may often be seen and felt through 

 the wall of the belly, as a violent writhing 

 peristalsis. After a variable period, vomiting 

 either occurs for the first time, or if already 

 present from other causes, it becomes faecal. 

 But peristalsis in an obstructed tube dis- 

 tended with fluid, not only implies a forward 

 movement in the particles that occupy its peri- 

 phery, but also necessitates more or less of a 

 backward current in those which are situated 

 in the axis or centre of the canal. And the 

 uniform consistence of the distending fluid, or 

 the return of solid fgeces, through many feet of 

 tortuous bowel, into theupper part of thecanal, 

 constitute frequent phenomena, which are best 

 explained by the mixture and circulation that 

 these two currents must tend to establish. 

 On the faecal fluid reaching the stomach, vo- 

 miting is excited. And it is scarcely neces- 

 sary to add, that this latter process, as usual, 

 involves the more or less complete evacuation 

 not only of the stomach, but also of the upper 

 part of the distended small intestine. 



Mucous membrane. Having thus briefly 

 described the peritoneal and muscular coats 

 of the small intestine, we may next proceed 

 to consider its mucous membrane: the struc- 

 ture on which its various functions essentially 

 depend. 



