124 THE BODY AT WORK 



tissues with which they are linked in harmonious co-operation. 

 The active principles of internal secretions have been termed 

 " hormones " from 6p/jt,da>, I announce. The glands of the 

 pyloric mucous membrane secrete a hormone which calls upon 

 the rest of the membrane to pour out gastric juice (cf. p. 89). 



What induces the cells of the pyloric mucous membrane to 

 produce the gastric hormone ? Their activity in this respect 

 evidently depends upon the presence in the stomach of par- 

 tially digested proteid substances. The cells judge, as it were, 

 when these substances come into contact with them, that there 

 is more work for the great bag of the stomach to do. They 

 call upon the part which is most active in secreting gastric 

 juice to pour it out quickly and get the business of digestion 

 over. Meat-extracts, which contain the products of protein 

 disintegration, have a similar influence in promoting the forma- 

 tion of the hormone. Hence, no doubt, the general custom, 

 found from experience to be beneficial, of commencing dinner 

 with soup ; although it must be remembered that the rapid 

 absorption of meat-extracts makes them peculiarly valuable 

 as restoratives. They afford very little energy, but what the} 7 

 have to give is quickly placed at the disposal of the economy. 

 Persons whose stomachs are unduly irritable are advised to 

 avoid soup. It leads to undesirable activity on the part of 

 the gastric glands, and especially of the acid-secreting cells. 

 Well-chewed bread also encourages the production of the 

 hormone. 



Here it may be well to call attention to the evident division 

 of the stomach into two parts the large bag, or cardiac portion, 

 which hangs down ; and the smaller, funnel-shaped pyloric 

 end, which is almost vertical. The distinction between 

 these two parts is faintly visible in the resting stomach, but 

 even opening the abdomen tends to obliterate it. That 

 it is much more evident during active digestion has been 

 shown by adding subnitrate of bismuth to the food, and 

 throwing the shadow of the stomach on a screen with Rontgen 

 rays. When this is done, it is seen that the two parts work in 

 different ways. Food is churned round and round in the 

 cardiac portion, and pressed towards the pylorus. Its fluid 

 products, mixed with the abundant secretion of the gastric 

 mucous membrane, are wrung out of it by the pyloric funnel. 



