Each of the four divisions of the ruminant stomach has its characteristic types of movement, as described by Wester (1926), Czepa & Stigler (1926, 1929, Mangold & Klein (1927), Schalk & Amadon (1928), and Phillipson (1939). Closely related to reticulo-ruminal motility is the phenomenon of rumination, shown by Stigler (1931, 1933, 1949) to be carried out by coordinated activity of the stomach and oesophagus with the respiratory apparatus. The existence of a nervous co-ordinating mechanism for gastric movements in the ruminant has been suggested by experiments of Ellenberger (1883), Wester (1926), Mangold & Klein (1927), Lagerlof & Hoflund (1936) and Hoflund (1940). The evidence, however, was incomplete; Mangold & Klein relied upon observations on laparotomized, anaesthetized animals, and on post-mortem findings after chronic neurectomies, while Hofilund based his observations on the auscultation of ruminal sounds and on post-mortem examination following section of various combinations of branches of the abdominal vagi.A detailed study has been made of the effects on reticulo-ruminal and abomasal motility of total and partial vagotomy and of splanchnotomy, and the results are described in this paper. METHODSThe work was carried out on lambs and adult sheep, mainly Scottish Blackfaces, with a few Cheviots and cross-breds; only two experiments were performed on calves, since they proved to be less suitable subjects. In order to avoid complications from initial ruminal paresis, about half the experiments were carried out on suckling lambs. They were received at 1-4 days of age, and were bottle-fed with a mixture of cows' milk with added casein and sodium citrate. Gastric motility was studied radiographically after the addition of barium sulphate to the milk mixture.
The number of published papers dealing with the pharmacology of the ruminant stomach is still small. An approach was made to the subject by Wester (1926), and later work includes that of Amadon (1930), Dougherty (1942) and the South African group, Quin & van der Wath (1938), Quin & Clark (1946 and Clark (1950a). The effects of choline esters and adrenaline were studied by Brunaud, Dussardier & Labouche (1950) and Brunaud & Dussardier (1951, 1953. The subject was reviewed by Clark (1950b). Except by Brunaud et al. (1950) most attention so far has been given to the responses of the rumen, and for this reason an extension of study to other parts of the stomach was needed.Because the work described here was done primarily as part of a wider study of gastric motility in the sheep, only those substances were studied which are believed to take part in the transmission of nerve impulses and to act as local hormones. Observations were also made on surviving gastric musculature in vitro. MATERIAL AND METHODSExperiments wita sheep. Scottish Blackface wethers were provided with ruminal and abomasal cannulae, usually of the ebonite type as described by Phillipson & Innes (1939), and were trained to stand quietly in a metabolism crate. Gastric motility was transmitted to air-filled rubber balloons and water manometers, pressure changes being recorded on a smoked paper. The ruminal cannulae had an internal diameter ofabout 2 cm And allowed simultaneous recording from balloons in the reticulum and rumen. The polythene tube connecting the reticulum balloon to the manometer system was supported by a stiff wire bent to allow the balloon to be passed through the rumino-reticular orifice. The rumen balloon was placed in the dorsal sac within a short distance of the cannula. A more sensitive, thin rubber balloon was preferred for the abomasum and this was placed in the mid-region of the organ. Two manometers were used and simultaneous records were made from any two of the three sites described.The average weight of the sheep was 30 kg. Each substance was given to at least six sheep, and usually at least 48 hr elapsed between successive experiments on one sheep. Four sheep were used for pharmacological experiments after bilateral thoracic vagotomy, combined in three with bilateral splanchnic section; the history of these sheep has been given in an earlier paper (Duncan, 1953). One adrenalectomized ewe was made available by Mr J. V. R. Evans. Two sheep and a goat were used for acute experiments during which they were anaesthetized with sodium pentobarbitone.
The state of motor activity of the stomach was studied in a series of foetal sheep. The non-functional period was found to end between the 50th and 60th days of gestation. Sustained activity was preceded by short periods of myogenic and neuromotor activity, and was not in evidence until the 70th day. Foetal swallowing commenced soon after this, but the pattern of suckling behaviour developed gradually over an extended period. The motor mechanisms mediated by the vagus were studied by section and electrical stimulation of the nerve.
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