LABORATORY WORK 189 



calcium chloride. Large and vigorous beats will be obtained, 

 lasting for several hours. 



Sources of Energy 



Connect an inverted funnel, held in a clamp, to a wash-bottle 

 containing lime-water. Bring under the funnel a piece of sugar or 

 a bit of fat which has been set burning on iron gauze by aid of a 

 Bunsen burner. At the same time suck the products of combus- 

 tion through the wash-bottle. The lime-water becomes milky. 

 Note that by burning food materials in air we obtain carbon 

 dioxide and energy (heat) just as when burned (oxidised) in a 

 more gentle way in the living organism. 



Alimentary Canal of Frog and Rabbit 



Opening a pithed or chloroformed frog along the middle ventral 

 aspect, notice 



The gullet (cesophagus), leading from the back of the mouth 



to the stomach. 

 The stomach. 

 The narrow, small intestine, passing from the stomach and 



forming a few coils before opening into the broader. 

 Large intestine. 



The large brown liver, with its gall bladder containing bile. 

 The pancreas, a small pale yellow organ near the beginning 



of the small intestine. 



In a rabbit, killed by chloroform, the same organs will be 

 better seen. The pancreas is more diffuse. The beginning of 

 the large intestine has a voluminous sac, full of food material, 

 attached to it ; this is the caecum, which is exceptionally large 

 in herbivorous animals. Careful dissection will show the duct 

 from the pancreas, opening into the small intestine about two 

 or" three inches from the stomach. 



Enzymes and Digestion 



Rates of Reactions. I. Add a small quantity of silver nitrate 

 solution to a beaker of dilute sodium chloride solution. A pre- 

 cipitate of silver chloride falls instantly. 



2. Add i or 2 c.c. of methyl acetate to a beaker of water, con- 

 taining a few drops of an alcoholic solution of phenol-phthalein. 

 Add dilute sodium hydroxide, drop by drop, until the colour 

 turns red. We have now an excess of alkali present. This is 

 capable of decomposing the ester into acetic acid and methyl 



