. Public health laboratory work, including methods employed in bacteriological research, with special reference to the examination of air, water and food contributed . y have been originally pre-sent, sufficiently pure to respond to tests—the best ofwhich is: — 7. Pour on to the residue a few drops of a mixture ofequal parts of pure carbolic and sulphuric acids—when,if the poison be present, an orange red or purple colourappears. In the case of cheese and butter, these are firstthoroughly worked up—triturated—with water, whichis then treated in the manner indicated above. 306 LABORATORY WORK.
. Public health laboratory work, including methods employed in bacteriological research, with special reference to the examination of air, water and food contributed . y have been originally pre-sent, sufficiently pure to respond to tests—the best ofwhich is: — 7. Pour on to the residue a few drops of a mixture ofequal parts of pure carbolic and sulphuric acids—when,if the poison be present, an orange red or purple colourappears. In the case of cheese and butter, these are firstthoroughly worked up—triturated—with water, whichis then treated in the manner indicated above. 306 LABORATORY WORK. CHAPTER V. Corn—Wheat-flour. Corn.—This term includes the seeds of cereal plantsin general, and it is of primary importance, in foodanalysis, that the knowledge shall be acquired wherebyit becomes possible to distinguish between the differentseeds, whether in a w^hole or ground state. The appearance of the complete seeds is so generallywell known that a description is not required here, andit is, moreover, almost entirely in the form of flour —, when these seeds are finely ground,—that theHealth Officer is concerned with them. Before, how-. FiG. 54.— The corn Weevil (Calandra granaria).(Magnified and natural size). ever, dismissing the subject, certain abnormal con-ditions of the seed, which are brought about bysmall animal and vegetable parasites, should beconsidered. Those presenting minute round perforations, and con-sisting almost entirely of a shell, show that the seed hasbeen penetrated and its bulk removed by a small insect,visible to the naked eye, termed calandra granaria {videfig. 54) and popularly known as the weevil. Those which are discoloured, and in which the bulkof their substance is replaced by a fine cottony material, CORN WHEAT FLOUR. 307 have been attacked by the ear-cockle or vibrio tvitici—a small worm-like parasite, pointed at either end asshown in figure 55.
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