§3.112 VISCERAL MUSCLE 63 



24 hours, if perfused with a suitable Ringer sohition. In Pcri- 

 planeta, an extract of one pair of its own corpora cardiaca to 

 10 ml Ringer solution causes the rate of peristalsis in the hind-gut 

 to be doubled, and stronger solutions have more marked effects; 

 but the peristalsis of the fore-gut seems to be inhibited. It is 

 certain, at least in Periplaneta and in the locust, that increase in 

 peristalsis of the Malpighian tubules can also be induced by a 

 substance from the corpus cardiacum, as well as possibly one from 

 the brain. The latter observation requires confirmation, in view 

 of Cameron's finding that the neurosecretion from the brain 

 does not contain the active principle causing heart muscle 

 contraction. 



Vertebrata. The visceral muscle of the vertebrate gut is mainly 

 under the dual control of the nerves of the sympathetic and 

 parasympathetic systems working in opposition ; but the effect of 

 the former can also be brought about in emergency by adrenaline 

 from the adrenal medulla. 



Cold-blooded vertebrates. The effects of adrenaline appear 

 to depend upon dosage. In the frog, Rana, small doses stimulate 

 the contraction of gut muscles ; but larger doses inhibit it (Budden- 

 brock, 1950). 



Mammalia. Adrenaline, secreted in response to excitement 

 or fear, contracts the sphincter muscles of the gut and inhibits 

 peristalsis, as can be shown by adding blood from an excited cat 

 to the Ringer solution in which isolated gut muscle is contracting 

 rhythmically (Fig. 3-3). Both reactions tend to stop digestion and 

 fit in with the emergency mobilization of the blood supply in the 

 somatic muscles. 



As its name implies, cholecystokinin contracts the muscles 

 of the gall-bladder in frogs and in most mammals. It may also 

 relax the sphincter muscle. The hormone therefore causes dis- 

 charge of the bile down the cystic duct, and appears to be the 

 only means of stimulating this reaction, for which there is no 

 nerve control (Grossman, 1950). It can be extracted from the 

 duodenal mucosa, and in nature is secreted in response to the 

 presence of fat, or fatty and other acids, in the duodenum. Its 

 histological origin has not been determined, but it appears to be 

 derived from endodermal cells, like secretin, and therefore not 



