182 



PRACTICAL PHYSIOLOGY 



The individual should now retire and open his bowels. On 

 returning a tracing of the colon should again be made. The whole 

 of the large intestine will be seen to have taken part in the act, even 

 the caecum being less full than it was before. In most cases every- 

 thing beyond the splenic flexure is evacuated in defaecation (Fig. 171). 



The above description refers to an average individual. Very 

 considerable variations occur between different people ; sometimes, 

 for example, the whole of the barium is collected in the pelvic colon 

 at the examination on the second morning, the rest of the colon 



10.30a.m., immediately 

 before defcecation. 



10.35a.m., immediately 

 after defcecation. 



12.20 p.m. 



FIG. 171. Defaecation. 



being invisible. Remarkable variations in the shape, size, and 

 position of the different parts of the alimentary canal are also 

 observed in perfectly normal individuals. 



Care should be taken to expose the body, and especially the hands 

 and the testicles, to the rays for as short a time as possible. So long 

 as no part of the body is subjected to the direct action of the rays 

 for more than ten minutes during the three examinations, it is 

 unnecessary to wear any special protective covering. 



