DIGESTION AND RESORPTION 85 



or 1 8 days. This would be not at all favourable for 

 the animal. Then Nature would proceed in a much 

 more advantageous manner if it digested the food 

 in portions successively. This is in fact the case. 

 If an animal takes a certain quantity of solid food, 

 e.g. flesh, it is spread over the interior of the 

 stomach in layers, so that the food first taken forms 

 the layer nearest to the walls of the stomach and the 

 innermost layer contains the food eaten at the end. 

 This is shown in experiments by Ellenberger and 

 Grutzner. The gastric juice, secreted from glands 

 in the stomachical walls, diffuses extremely slowly 

 into the interior parts of the food. Therefore at 

 first the outermost layer is digested and carried away 

 through the pylorus, after which the digestion of 

 the second layer is carried to an end and its 

 digestion products carried away, and so forth until 

 the innermost layer is also ready. After this the 

 secretion of the gastric juice, which has gone on 

 during this whole time, comes to an abrupt end. In 

 this process also a part of undigested food is carried 

 away and without doubt digested later on in the 

 digestive tract. Therefore when the calculation in- 

 dicates that only a small quantity of food is left 

 undigested in the stomach, the experiment shows 

 that the stomach is really empty. This occurs, for 

 instance, in the experiments of London with dogs of 

 25 kilogrammes when less than 3 grammes of flesh 

 are left. 



From an inspection of column 5 in the table 

 giving Khigine's experiments we find that the time 



