PRACTICAL EXERCISES 383 



10.* Time required for Digestion and Absorption of various Food 

 Substances. Feed three dogs, A, B and C, which have previously 

 fasted for twenty-four hours, with a meal containing starch (proved 

 to be free from sugar), lard and meat. 



(1) After fifteen minutes inject subcutaneously into A 2 c.c. of a 

 O*T per cent, solution of apomorphine. Note the time which elapses 

 before the animal vomits. Collect the vomit. 



(a) Examine a little of it under the microscope, and make out fat 

 globules, muscular fibres and starch granules. The latter can be 

 recognised by their being coloured blue by a drop or two of iodine 

 solution. 



() Filter the chyme, mixing it, if necessary, with a little water, 

 and test it as in 4 (d] (p. 378) for the products of digestion of pro- 

 teids. In addition, test for starch, dextrin, and reducing sugar. 



(2) One and a quarter hours after the meal inject apomorphine 

 into dog B, and proceed as in (T). 



(3) Two and a half hours after the meal inject apomorphine into 

 dog C, and proceed as in (i). Compare the results from the three 

 specimens of chyme. 



ii. 1 * Quantity of Cane-sugar inverted and absorbed in a Given 

 Time. Take three dogs, A, B and C, which have fasted for twenty- 

 four hours. The animals should be about the same size. Feed A 

 and B with TOO c.c. of a standard solution of cane sugar (about a 10 

 per cent, solution). If the dogs have been kept without water for a 

 day they will more readily take the sugar solution. Or it may be 

 given through a tube passed into the stomach, and in this case a larger 

 quantity of sugar can be given. Feed C with 10 grammes of powdered 

 cane-sugar mixed with lard, the mixture being rolled into little balls. 



(i) After a quarter of an hour put A under chloroform or the ACE 

 mixture, and fasten it on a holder. Kill the animal with chloroform, 

 open the abdomen, lie the oesophagus, place double ligatures on the 

 pyloric end of the stomach and the lower end of the small intestine, 

 and divide between them. Cutout the stomach and intestine; wash 

 their contents into separate vessels, and test the reaction with litmus 

 paper. Add water and rub up thoroughly. Filter. Wash the residue 

 repeatedly with small quantities of water, and pass all the washings 

 through the filter. Make up each of the two filtrates to 200 c.c. 



(a) Test the filtrates from the contents of the stomach and intes- 

 tines qualitatively for glucose by Trommer's (p. 23) and the phenyl- 

 'hydrazine test (p. 431). 



(b) If no reducing sugar is present, add to 20 c.c. of each filtrate 

 i c.c. of hydrochloric acid, boil for half an hour, and again test for 

 reducing sugar. If it is now found, some cane-sugar is present. 



(t) If reducing sugar is found, estimate its amount as glucose by 

 Fehling's solution (p. 431) in a measured quantity of the filtrate 



* Experiments 10 and n are conveniently done in a class by assigning 

 each of the three animals to a separate set of students. The contents of 

 the stomach and intestine are divided into three portions, so that each 

 set has a sample from each dog. 



