107-109] EXPERIMENTS ON FEEDING MATERIALS 41 



EXPERIMENTS ON FEEDING MATERIALS 



The experiments described below show some of the 

 properties of feeding materials ; they are divided into four 

 sets, viz. experiments on oil-cakes, experiments on grass, 

 experiments on turnips, and experiments on cereal foods. 



Oil-cakes. 



107. The principal kinds of oil -cake are linseed cake 

 and cotton cake, but many other substances are used, 

 such as rape, palm-nut, and various flavouring materials. 

 The chemical constituents which affect the feeding value of 

 oil-cakes are much the same, whatever the seed used. 

 The constituents are water, oil, albuminoids, carbohydrates, 

 woody fibre, and sand, the last two forming the indigestible 

 part of the cake. The meaning of the above chemical terms 

 is explained as far as possible in the following experiments. 



108. Water in Oil-cakes.— Grind up a piece of lin- 

 seed-cake in a mortar and place a little of the powder in a 

 bulb-tube with a neck about eight inches long. Boil some 

 water in a small beaker standing on a wire gauze. Now 

 hold the bulb containing the cake just beneath the surface 

 of the boiling water in a slanting position, so that the bulb 

 and cake may be heated up to the boiling-point of water, 

 whilst the rest of the tube is kept cool. In a very short 

 time water-vapour will come off from the apparently dry 

 cake and condense in the cooler part of the tube, where it 

 may be seen to dim the inner surface of the glass tube. 



109. Oil in Oil-cakes. — Spread out a little linseed- 

 cake, which has been ground up in a mortar, on a piece of 

 filter-paper. Lay the paper on a clean white tile and just 

 moisten the cake with ether. After it has stood for a minute 

 exposed to the air, the greater part of the ether will have 

 evaporated. Place the paper for five minutes in the steam- 



