ELEMENTARY EXPERIMENTAL PHYSIOLOGY 20$ 



through the small intestine. A diffuse shadow is generally present at 

 this time in the pelvis. It consists of the terminal coils of the small 

 intestine, the last few inches of which can often be recognised as they 

 join the caecum. With a narrow diaphragm for the X-rays, short lengths 

 of intestine can generally be clearly defined and their movements studied. 

 A general forward movement of the shadow as a whole, due to 

 peristalsis can be recognised. At the same time segmentation is seen 

 to occur. The shadow of a short length of intestine, at first of uniform 

 thickness, becomes constricted in its centre. The constriction increases 

 until the single shadow is more or less completely divided into two. 

 Then each half undergoes a similar division, the two central segments 

 of the four produced by the second division joining together. The 



fo Umbilicus. 



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Flo. 198. -Segmentation of small intestine. 



new central segment then divides again, the segmentation continuing 

 at the rate of about seven divisions a minute. The process is shown 

 diagrammatically in Fig. 198. 



A further examination should be made on the following day as early 

 in the morning as convenient. If possible, the bowels should not be 

 opened before this examination. The whole of the large intestine is 

 generally visible, and its position should be marked out in the vertical 

 and in the horizontal position. In the horizontal position the trans- 

 verse colon is approximately on a level with the umbilicus; in the 

 vertical position it is considerably lower. Both the hepatic and 

 splenic flexures are generally acute, especially in the vertical position, 

 and the two limbs of the flexures may form a single shadow. The 

 effect of straining, as it occurs in defaecation, should be observed : the 



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