The animal nature of cochineal cannot be recognised by the naked eye, it is seen on examination under the microscope; this has given opportunity for the most incredible adulterations of the costly substance. Cases have been known in which a paste chiefly composed of flour has been pressed into the form of cochineal, the grains coloured by some cheap red colouring matter, powdered with the dust from boxes in which cochineal has been packed, and placed upon the market as cochineal. The expert would not be deceived by this gross fraud, but another method of adulteration is far more difficult to recognise; genuine cochineal is brought into commerce from which the greater part of the colouring matter has been extracted, and which has been again powdered with the grey cochineal dust. Such extracted cochineal does not produce the same brownish-red powder as the fresh substance. In the cochineal insect there is a very large quantity of colouring matter: it may reach 50 per cent. of the weight of the dry insect. The colouring matter, which is known as carmine (the same name is also applied to its lake), is soluble in water with a fine red colour. When cochineal is extracted with water the operation must be often repeated, and each time fresh quantities of colouring matter are dissolved. The cochineal may be exhausted by repeated boiling with water, but a large quantity of liquid containing little colouring matter is then produced. In order to obtain a strong solution of the colouring matter the cochineal must be powdered; this is difficult on account of the softness of the material, which does not give a fine powder, but a pasty mass. The object is best attained by grinding the cochineal through a mill similar to a coffee mill, but since the grooves of the steel cone, which effects the crushing, may be easily clogged, the mill must be arranged so that the cone can be taken out and cleaned.