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A MANUAL OF PHYSIOLOGY. 



II A.M 



fundus, so far as its mechanical functions are concerned, acts 

 chiefly as a reservoir for the food, which, like a hopper, it gradually 

 passes into the pyloric mill as digestion goes on by a tonic 

 contraction of its walls. The existence of this reservoir enables 

 larger quantities of food to be taken at one meal, which can then 



be digested gradually. These facts 

 have been mainly ascertained by ob- 

 servations on animals, such as the 

 dog and the cat, either by direct in- 

 spection after opening the abdomen 

 (Rossbach), or in the intact body, 

 under absolutely physiological condi- 

 tions, by means of the Rontgen rays 

 (Cannon). In the latter method the 

 food is mixed with subnitrate of 

 bismuth, which is opaque to these 

 rays, so that when the animal is looked 

 at through a fluorescent screen the 

 stomach appears as a dark shadow 

 in the field (Fig. 135). Even in the 

 excised stomach, kept in salt solution 

 at the body-temperature, the typical 

 movements can be observed proceed- 

 ing for some time. 



In the small intestine two kinds of 

 movements are to be seen : (i) Gentle, 

 swaying, ' pendulum ' movements, 

 sometimes irregular, but often recur- 

 ring rhythmically at the rate (in the 

 dog) of 10 or 12 in the minute. Both 

 the longitudinal and the circular mus- 

 cular coats contract, causing slight 

 waves of constriction, which may 

 FIG. I35 .-CAT' S STOMACH SEEN originate at any part of the gut, but, 

 BY RONTGEN RAYS (CANNON), under normal circumstances, nearly 

 [ The outlines of the stomach always travel from above downwards, 

 containing food mixed with bis- with a velocity of 2 to 5 centimetres 



p er 5^0^ These movements cause 

 the coils of the intestine to sway 

 gently from side to side. Under 

 abnormal conditions, as in the exposed ' surviving ' intes- 

 tines of the rabbit, contractions, probably similar to the 

 pendulum movements, but running indifferently in both direc- 

 tions, can be set up by local stimulation. The function 

 of these pendulum movements seems to be the thorough 

 mixing of the food with the digestive juices in the intestine. 



muth subnitrate were drawn 

 at intervals from n a.m. to 

 4.30 p.m. 



