CHAP. II.] DURATION OF GASTRIC DIGESTION. 159 



Duration of the Digestive Process in the Stomach. 



The digestive process varies' in duration in different animals, and 

 in the same animal according to the nature of the food, to its state 

 of division &c. In Alexis St Martin, Dr Beaumont found the 

 duration of the gastric digestive process to be between three to five 

 hours, and Richet remarks, as the result of his observations on his 

 patient Marcelin, that the digestive process does not appear to extend 

 beyond four or five hours, though three hours represent its more 

 usual duration \ 



In dogs and other carnivorous animals which are in the habit of 

 'bolting' large masses of meat, undigested masses are occasionally 

 found in the stomach eight or ten hours after a meal and often longer. 



In connection with this question we have to consider the facts 

 which relate to the manner in which the stomach empties itself. 



According to some physiologists, almost from the earliest mo- 

 ments of gastric digestion, the patulous pyloric orifice allows the soft, 

 already chymified portions of the contents, to escape into the duo- 

 denum, whilst the yet solid contents, not being able to escape, are 

 mechanically retained and forced to revolve and revolve, until, under 

 the influence of fresh juice, of the heat, of the mechanical move- 

 ments of the compressing stomach, they themselves break down into, 

 and form part, of the grumous chymified mass. 



By a gradual process, then, the stomach, according to this view, 

 gradually empties itself. 



The author is not disposed to believe that matters proceed pre- 

 cisely in this manner, but rather as has been described by Richet and 

 by Kiihne. 



According to Richet, whilst doubtless the softer and more dif- 

 fluent portion of the gastric contents do, little by little, escape from 

 the stomach into the duodenum, the quantity thus escaping is in- 

 significant, the stomach contents remaining essentially undiminished 

 during the average digestive period of three hours, at the conclusion 

 of which, within a very short time, the whole of the contents are 

 emptied into the duodenum. 



The process, according to Kiihne, is very similar in the dog, 

 except that the average duration of gastric digestion is five, and not 

 three, hours. During these five hours, at intervals of about ten 

 minutes, the stomach expels small quantities of its contents through 

 the pylorus ; the great mass remains, however, to be expelled, almost 

 at one time, when the act of gastric digestion comes to an end. 



1 The reader is referred to a very interesting set of observations, on the duration of 

 the digestive process in a thoroughly healthy man of 30, made by Jessen. The 

 duration of the digestive process was judged of by the stomach-pump. 100 grammes 

 of raw beef + 1 gramme of salt and 300 c.c. of water were digested in 2 hours. If the 

 meat were thoroughly boiled or roasted (underdone) the time occupied in digestion 

 was 3 hours. 



602 c.c. of fresh unboiled cow's milk were completely digested in 3 hours, but 

 the same quantity of boiled cow's milk required 4 hours (Zeitschrift fur Biologic, Vol. 

 xix. (1883), p. 149). 



