1 84 THE ENGINES OF THE HUMAN BODY 



stances. A dish of cornflour will be passed onwards in 

 the space of two hours or less, while a Christmas dinner 

 of roast goose and plum pudding is likely to keep the 

 discharge system of the stomach hard at work for three 

 times that period. Youth, too, makes a difference ; in 

 the young the stomach is vigorous and usually effective. 

 In certain disorders of the transport system a new meal 

 arrives long before its predecessor has been discharged. 

 Twelve hours or more may elapse before its bismuth 

 shadow disappears. The condition of mind, a feeling of 

 well-being, has a direct and immediate influence on the 

 transport system of the stomach. That digestion waits 

 on appetite is a truth man has known since he became a 

 thinking being. Indeed, the study of the movements of 

 the stomach by means of X-rays and bismuth meals was 

 first practised by Professor W. B. Cannon to discover 

 how far the state of the brain could influence the work of 

 the stomach. He was a student of Harvard University 

 in 1896 when ROntgen's discovery was announced, and 

 saw the possibility of studying the normal healthy stomach 

 in a new way. He selected the cat as the subject for 

 observation, and was the first to succeed in seeing the 

 movements of the living stomach by means of X-rays. 

 When the cat was made angry the movements of the 

 stomach ceased ; when made to purr, they commenced and 

 worked more vigorously than usual. Although the will 

 can exercise no direct control over the muscular engines 

 which carry on the transport system of the stomach, yet 

 indirectly it can influence and play upon the elaborate 

 nerve system which controls its movements. 



In the meantime we must not lose sight of the main 

 object we have in view — the preparation of body-fuel 

 from the food we eat. We have seen how it is masticated 

 and pulped in the mouth, and how it is transported to 

 the stomach, and we have watched the shadow of that 

 organ during the four hours in which its preparatory 

 changes were going on. We shall now give our living 

 model a rest, recalling him in the afternoon to see what 

 progress the bismuth meal has made, and in the meantime 



