226 GENERAL SCIENCE 



free hydrochloric acid. The casein in curdling gathers up much of 

 the butter-fat present in the milt. 



Milk should contain about 4 per cent of butter-fat, and 86 per cent 

 water. There is considerable sugar of milk in it, a matter of importance 

 in preparing foods for infants. 



In preparing sausage for sale it is a common practice to mix in with 

 the lean and fat meat as ground together more or less of starchy mate- 

 rial. As a "filler" this increases the weight of the product, and at the 

 same time by absorption of the moisture contributes to the keeping 

 quality of the sausage. It is a cheaper material than meat, and so 

 may be regarded as an adulterant. The use of preservatives in meats 

 interferes with their digestion when eaten, and they may be positively 

 harmful in the system. 



THE CARBOHYDRATES 



The botanist notes in the green coloring of vegetation the 

 presence of chlorophyll. The little bodies containing this 

 chlorophyll as found in the protoplasm of the cells of the 

 plant are known as chloroplasts. In them the water from 

 the ground and the carbon dioxide from the air are being 

 manufactured directly or indirectly into sugar, starch, and 

 cellulose (wood fibre) by use of the energy derived from sun- 

 light. Animals appropriate and use these products of 

 chemical change in plants, but only plants can produce them 

 from the raw materials! 



It has been found by botanists that plants as well as 

 animals must have oxygen to live, i.e., to maintain the life 

 of the protoplasm. A product of the processes of plant 

 life as a whole is a relatively small quantity of carbon 

 dioxide gas. This shows that the process of oxidation goes 

 on in plants even as in animals, though much more slowly. 

 During the daytime, and under the influence of sunlight, 

 this action may be completely masked by the fact that 

 carbon dioxide obtained from the air is at the same time 

 being chemically combined with water in the plant. A prod- 

 uct of this change is a relatively large amount of oxygen 



