STOMACH AND INTESTINE. 



343 



the intestines generally gives them a nodu- 

 lated or almost moniliform shape, and the 

 movement gradually ceases. On uncovering 

 portions of the canal hitherto concealed, all 

 these appearances are repeated. The con- 

 tracted state remains for some hours, and 

 finally again disappears. 



Now the tranquillity cf these portions of 

 intestine previously to the admission of air, 

 the irregular and diffuse nature of the con- 

 tractions themselves, the final result on the 

 intestine, and the effect of uncovering fresh 

 portions all these circumstances together 

 offer the strongest probability, that the move- 

 ments witnessed are due to the contact of the 

 air. And hence, although it is interesting to 

 notice that these contractions often assume 

 the form of a peristalsis (that is, of a circu'ar 

 constriction which travels slowly in a direc- 

 tion towards the rectum), still they do not 

 warrant any conclusions as to the nature or 

 force of those definite movements which are 

 doubtless executed by the intestines during 

 life. 



Nor are the movements which result from 

 applying a local irritation to the bowel, under 

 the same circumstances, much more uniform 

 or conclusive. Unless excited before the 

 commencement of the vermicular movements, 

 or towards their close, they are obviously 

 liable to be confused with these; which, 

 indeed, they closely resemble. Thus, when 

 the surface of the bowel is irritated mechani- 

 cally, a mere local contraction is sometimes 

 produced. In other instances, and especially 

 when the duodenum is the part attacked, 

 the contraction extends downwards, or even 

 upwards, from the irritated point. Sometimes 

 this diffused contraction occurs almost imme- 

 diately after the application of the stimulus ; 

 sometimes only after the lapse of a consi- 

 derable interval of time. Sometimes, without 

 any repetition of the stimulus, such waves are 

 repeated; with short intermissions, and of 

 gradually diminishing strength. Sometimes, 

 instead of one continuous wave, a broken or 

 interrupted one is produced; a condition 

 which is chiefly seen in the small intestine. 

 Similar contractions may also be excited by 

 the mechanical or chemical irritation of the 

 nerves which immediately supply the intes- 

 tines. But irritation of the mucous membrane 

 has little or no effect. Direct galvanic stimu- 

 lation, by means of the rotary electro-magnetic 

 apparatus, repeats many of these appearances. 

 On applying the approximated electrodes to a 

 given point, a short interval precedes the occur- 

 rence of a local contraction : and this con- 

 traction endures after their removal. In some 

 animals, this local contraction is jwly propa- 

 gated onwards, for a variable distance, towards 

 the rectum. This continuous movement may 

 even be repeated without any fresh appli- 

 cation of the stimulus. But that more diffuse 

 irritation which may be produced by stroking 

 the intestine with the wires gives rise to 

 none but local contractions. While galvanizing 

 the nerves reproduces the lively, but general, 

 movements above alluded to. And finally, 



whatever be the form of irritation, it ceases to 

 have any effect, soon after the lapse of that 

 period at which the vermicular movements 

 usually cease. This departure of irritability 

 may, however, be retarded by warmth, or by 

 preventing the access of air. And the capacity 

 for such movements may sometimes be re- 

 stored by returning the divided and dead 

 intestine to the belly of the living animal. 

 Finally, though the repeated irritation of any 

 one part soon exhausts its contractility, still, 

 after a short interval of repose, it is at least 

 partially restored. 



On mechanically irritating the exposed 

 intestines of the living animal, very different 

 results are obtained. Compressing them 

 between the fingers produces a local con- 

 traction, which bjsts some few minutes, and 

 then disappears. Scratching their peritoneal 

 surface usually gives rise to elevations, which 

 are just as local as the preceding depressions. 

 These elevations, which seem to be due to 

 relaxation of the outer or longitudinal mus- 

 cular layer, are accompanied by contractions 

 of the deeper transverse fibres. And the latter 

 can still be excited, after all possibility of pro- 

 ducing the former has been destroyed by 

 cold. Mechanical or chemical irritation of 

 the mucous membrane, or pinching or section 

 of the nerves, produces no movements what- 

 ever : even where the degree of nervous sti- 

 mulation is such as to cause convulsive move- 

 ments of the hind feet of the animal. And 

 distention of the bowel with water seems to 

 be equally inefficacious; indeed, it appears to 

 leave the ordinary irritability by local stimuli 

 very little affected. 



The observations of Schwarzenbcrg and 

 Ludwig *, upon dogs in whom intestinal 

 fistulse had been carefully instituted, afford 

 much more direct and trustworthy evidence 

 respecting the normal intestinal movements. 

 They introduced into the canal balls of wax, 

 attached to slender lead wires ; and thus 

 verified the following details. The contents 

 of the canal are propelled by a slow continuous 

 peristalsis, which has a definite direction 

 towards the rectum. And although irritation 

 always excites a local contraction, it only 

 gives rise to peristalsis at definite times, 

 during the intervals of which the intestine 

 remains at rest. These times have a general 

 connection with the digestive act: the period 

 of minimum activity being before a meal ; 

 while the maximum of movement is usually 

 from four to six hours after it. But the act 

 of peristalsis is essentially independent of the 

 presence of food ; since it may be produced 

 in a starving animal, or in an empty segment 

 of tube. And not only does this intermittent 

 character affect the general occurrence of the 

 propulsive act, but even, to all appearance, 

 its specific phenomena. For when applied at 

 the proper period, a single continuous irri- 

 tation produces a repeated and intermittent 

 peristalsis. Hence it is obvious that, during 



* ZeitschriftfuerdieRationellenPathologie,Bd.vii. 

 p. 315. 



z 4 



