The progress of food through the alimentary canal was studied by X-rays and the results are summarised in Fig. 12.

The movements of the crop and gizzard were recorded graphically. Those of the crop did not conform to a constant type of rhythm and they were, unlike the gizzard contractions, influenced markedly by impulses from the higher centres. The fasting fowl was very sensitive to pressure changes in the crop but not to those in the gizzard. The rate of contraction of the gizzard was about 2.5 per minute and it was increased to about 3 per minute by ingestion of food irrespective of its nature. The effect of drugs on the movements of the gizzard led to the opinion that they are controlled by the vagus and sympathetic nerves.

The blood-sugar of fowls was studied during fasting and after various kinds of carbohydrate-rich foods. After a preliminary fall, it rose on the third and fourth day of fasting to fall again sharply to a slightly subnormal level, about which it remained until the end of the seventh day. A change in the type of energy metabolism is suggested as the probable cause of these fluctuations. The nature of the hyperglycaemia following diets containing cellulose in varying states of division, confirmed the view, already expressed, that the gizzard functions as a filter, in such a way that fine material enters the duodenum in about I min. after ingestion while coarse material is retained much longer to be ground by the contractions of the organ. Within 5 min. after ingestion of a starchy meal the blood-sugar rose distinctly, thus suggesting correspondingly rapid hydrolysis of starch and absorption of glucose. The absorption coefficient of glucose was found to be 0.209, and evidence was obtained suggesting that there is probably an optimal solution for absorption at a concentration nearer 0.75 M than 2 M. The changes in blood-sugar and in liver glycogen corresponded with the rate at which glucose was absorbed.

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