ii CHANGE OF FORM IN MUSCLE DURING ACTIVITY 171 



course, it exhibits later on an increasing diminution and retarda- 

 tion of the wave, in proportion with the distance from the starting- 

 point, until finally only a local constriction remains visible. 



The reaction of the intestine is thus in complete conformity 

 with that of the ureter. As Engelmann has made analogous 

 observations upon the stomach and intestine of rats, mice, 

 pigeons (most elegant), the oesophagus, stomach, and intestine 

 of frog, and uterus and vagina of pregnant rabbits, the conclusion 

 may be accepted that in all cases in which peristaltic movements 

 can be provoked, anti-peristaltic contraction is also at least possible. 

 It must be admitted, on the other hand, that conductivity of 

 excitation within the muscular coat of the intestine is frequently 

 absent, when it might more reasonably be expected. This occurs 

 more particularly when the abdominal cavity is opened in warm 

 salt solution, when the intestine usually remains perfectly 

 quiescent. If under these approximately normal conditions 

 any point is stimulated mechanically by gentle pressure, or 

 ligature, only a local, circular constriction will appear (as 

 stated by van Braam - Honckgeest (30) and confirmed by 

 Nothnagel (31)), which is confined to the seat of excitation, and 

 never spreads beyond it in a peristaltic or anti-peristaltic wave of 

 progression. As there is no reason to suppose that conductivity 

 is lower here than after bleeding the animal, from Engelmann's 

 point of view no other assumption is possible, but that the trans- 

 mission of excitation is blocked by a kind of inhibition, possibly 

 proceeding from the ganglionic plexus. And, experimentally, it 

 is impossible to deny the co-operation of nervous impulses, 

 whether of an inhibitory or motor nature, in intestinal peristalsis. 

 The question then arises whether the normal movements, i.e. the 

 propagation of a wave of contraction in one or the other direction, 

 may not be produced, in each point of the area traversed, by a 

 nervous impulse. It can, indeed, hardly be disputed that such 

 impulses must play a very important part in the discharge of the 

 contractions which usually follow in rapid succession. The extreme 

 slowness of transmission, which may be followed with the eye, can, 

 as already pointed out by Engelmann for the ureter, be urged 

 against the first view. On the other hand, it affords no better ex- 

 planation than Engelmann's theory of the localisation of excitation 

 effects in the perfectly normal intestine, or the sudden extinction of 

 a wave of contraction, as, e.g., often observed byNothnagel (I.e. p. 14). 



