4. =Color.= The color of an organ or part should be noted as soon as possible after its removal from the body, or, better, as soon as the cadaver is opened, since oxidation, evaporation, loss of blood, and contact with water quickly cause color-changes. Venous blood may quickly become bright red, notably in the spleen and cerebral veins and sinuses. It is not to be supposed that, even when the cadaver is opened within a very short time after death, the color is that of the living body. Certain color-changes always take place as soon as death occurs, but it is necessary to create a color-standard for the different organs as seen under the conditions of the ordinary autopsy. Injections of formalin and other undertaker’s fluids destroy all color, and should not be permitted before the autopsy. Freezing likewise changes the color of many of the organs. The judgment of the color of the tissues and organs of the human body is extremely difficult because of the fact that only rarely is a pure simple color seen. Ordinarily a combination of colors is present, and the analysis of these is often not easy. If the organ is held before the eyes at a distance of about a yard an impression of a single color-unity may be obtained, but when brought nearer to the eyes the surface presents a variegated, mottled, speckled or streaked effect of many colors, sometimes running the entire range of the spectrum. The colors most frequently seen in the body are yellow, red and brown in all possible combinations and shades. Blue, gray, slate, black, green and purple are also common in combination with these three or with one another. The analysis of the color is concerned, first with the color proper of the parenchyma, secondly with the color of the blood and the blood-content, thirdly with the color of some pathologic substance contained in the tissue, as blood- or bile-pigment, carbon, melanin, etc. In describing color-combinations use the predominant color last; as, for example, a reddish-yellow-brown means that the predominant color is brown with more yellow in it than red. Innumerable combinations of these three colors exist (light brown, chocolate, yellowish-brown, brownish yellow, brownish red, etc.). The macroscopic color will not be apparent in microscopic preparations except when due to a true pigment.