Morphological, chemical and mechanical aspects of the excitation and contraction in the visceral smooth muscle, concerning chiefly with the results obtained in our laboratory, were reviewed.
There exsist essentially no qualitative differences between the nature of the contractile proteins of the smooth muscle and those of the skeletal muscle. Some quantitative differences between these proteins and their location (arrangement) in the cell, however, seem to be the characteristics of the smooth muscle.
From the results in the biochemical experiments on the vesicular system, probably including mitochondria, of the smooth muscle, it was suggested that this system has a pumping function extruding Ca ion from the cell. Further investigations would be the important key in the investigation of the E-C link mechanism.
On the other hand, it has been reported that the presence of the extracellular Ca is extremely important in the excitation and contraction of the smooth muscle. These results indicate that extracellular Ca fluxes into the cell during the excitation of the membrane and activates directly the contractile proteins.
The characteristic mechanism which induces the contraction of the smooth muscle was discussed.

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In this report, it was intended to analyze gastric and duodenal action potentials with use of the medical computer.
Ten mongrel dogs weighing about 10 kg were used for the experiments. Under the anesthesia with pentotal sodium administered intravenously or intraperitoneally, abdominal cavity was opened.
Bipolar platinum-electrodes were implanted into subserosal tissue of the antrum for the recording of action potentials of the stomach.
After the transverse incision and re-anastomosis of the anterior wall of the duodenum at the mid-point between the pyloric ring and ampulla of Vater, two bipolar electrodes were implanted on both side of the anastomosed line, respectively. For recording of the action potentials, ‘ TIAC R-351’ was used.
‘Interval histogram’ and‘ distribution histogram’ of data were made with medical computer ‘ATAC 501-20’.
1) It was shown that intervals were distributed between about 12 to 14 seconds by non-sequential interval histogram of gastric action potentials.
2) In non-sequential interval histogram, interval time of duodenal action potentials in the control group were divided to two groups, namely the one was 0.1-1.0 seconds, the other was 2-8 seconds.
3) In non-sequential interval histogram, interval times of duodenal action poten-tial recorded at the distal portion of anastomosis were divided into two groups, the one was 0.5-3 seconds, the other was 3-9.5 seconds.
4) Distribution histogram of duodenal action potentials in the control group counted to about 82.5 spikes in one spike burst.

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The intrinsic innervation of the gastric musculature of the amphibia and mammals has been studied using histochemical techniques for the localization of both cate-cholamines and acetylcholinesterases (AchE), and by electron microscopical technique. 1) In both species, myenteric (Auerbach's) plexuses contain mostly cholinergic ganglion cells and fibers, together with fluorescent nerve fibers. The catecholamine-containing nerve fiber running in musculature appears to be associated with cholinergic ganglion cells in Auerbach's plexus or blood vessels. No catecholamine-containing ganglion cells were found in Auerbach's plexus. 2) In frog's stomach, very rarely, fluorescent nerve fibers are present in Auerbach's plexus. In toad's gastric musculature sometimes cholinergic axon containing both large (1000-1500 A) and small (350-600 A) granular vesicles was observed, electron microscopically. These kinds of granulated vesicle were not depleted by reserpine. 3) The distribution and density of cholinergic nerve elements vary in the three anatomical regions of toad's stomach. The muscle coat in Pars cardiaca is the most richly innervated part of the stomach and the musculature in Pars mpylorica receives denser innervation than in Corpus ventriculi. The smooth muscle in small curvature also has plenty of cholinergic innervation more than in large curvature. The regional differences in the richness of the cholinergic innervation are closely concerned with the distribution of the membrane resting potential values. 3) Ultrastructural finding also shows that circular muscle coat in toad's stomach especially receives an extensive and heavy cholinergic innervation by close neuromuscular junctions, but not in mammals. Functional myo-myo contact was richly present in mammalian stomach musculature, but not in frog's stomach. It is conceivable that smooth muscle in toad's stomach may belong to multiunit or neurogenic type, while mammalian gastric muscle exhibits a tendency to visceral or myogenic muscle type.

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Electrical activity was recorded from the stomach, duodenum, jejunum and ileum of 8 mongrel dogs which survived for more than two years after 90% massive bowel resections. Despite a considerable delay in gastric emptying time in the dogs with massive bowel resections, the electrogram revealed no substantial difference between the electrical activities of the stomach in normal dogs and the dogs with massive bowel resections. The basic electrical rhythm in the jejunum orad to the anastomotic line was 15-17 cycles/min., and in the ileum caudad to the anastomosis was 8-12 cycles/min. This evidence indicates that the gradient of the slow wave rhythm is maintained even for more than two years after jejunoileal anastomosis and the frequency of the slow wave of the residual digestive tracts generally tend to decrease in compensatory stage.

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Schiller, DiDio and Anderson reported that removal of 1 cm segments of longitudinal muscle coat in small intestine produced a sphincter-like action and delayed the transit time. To verify their report, the author performed 90% massivebowel resections in 35 mongrel dogs. In 10 dogs out of 35, reversed jejunalsegments, 10 cm in length, were interposed. In 9 dogs, circumferential removal of 1 cm strip of longitudinal muscle coat was performed proximal to the jejunoileal anastomosis according to the Anderson's technique. In 8 dogs, two of these “artificial sphincters” were situated 5 cm proximal to the jejunoileal anastomosis. In the remaining 8 dogs, no attempt was made surgically to delay the transit time. The longest survival time in animals with reversed jejunal segments was 9 months. Five animals out of 9 with circumferential removal of 1 cm strip of longitudinal muscle coat survived for more than two years and 3 control dogs survived over two years. It was found that the attempt to delay transit time of the bowel by producing the Anderson's stripped area was unsatisfactory, and that, at the present time, no definite operative measure is available to control short bowel syndrome.

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