210 



PRACTICAL PHYSIOLOGY 



whole of the colon is greatly depressed, the caecum and ascending colon 

 together forming a rounded shadow. Peristalsis is never seen, owing 

 to the extremely slow progress of the waves. 



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 everything beyond 

 the splenic flexure is evacuated in defaecation (Fig. 199). 



The above description refers to an average case. Very considerable 

 variations occur between different individuals ; sometimes, for example, 

 the whole of the bismuth is collected in the pelvic colon at the examina- 

 tion on the second morning, the rest of the colon being invisible. 



1 0.30 a.m., immediately 

 before defalcation. 





10.35 a.m., immediately 

 after defecation. 



12.20 p.m. 



FIG. 199. Defaecation. 



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. 



CHAPTER LVIII. 

 SALIVARY SECRETION. 



Salivary Secretion. DEMONSTRATION. The submaxillary gland is 

 situated within and a little behind the posterior angle of the lower jaw 

 bone. 



The animal anaesthetised with ether and chloroform is placed on its 

 back, and its head extended. An incision is then made along the 





