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Further Studies of the Relationships of the Structural Characters of Mammalian Hair

In the specimens of mammal hairs examined: (1) Scale-form (as expressed by the scale index, a mathematical expression of the relationship between the free proximo-distal diameter of the scales and the diameter of the hair-shaft) bore relation not to the natural group to which any given species belonged, but to the diameter of the hair-shaft. In other words, the coarser the hair the finer the scales, or the magnitudes of the free proximo-distal diameters of the cuticular scales and the diameters of the hair-shafts varied inversely. (2) The medulla-form varied with the diameters of the hair-shafts, and not with natural groups of mammals, in a definite way. (3) Hence, given the diameter of a hair-shaft, and regardless of the species from which it was derived, it should be possible to locate it in its proper medulla-form, or scale-form group, approximately. (4) It is inferred that the relationships between scale-form (as expressed by the scale index), medulla-form and hair-shaft diameter, which have been found in the series of samples examined in this study, obtain also among mammals in general. (5) From the results of previous studies of mammal hairs, as well as from added results from this present one, it can still be said, however, that specific differences of sufficient appreciable magnitude exist, commonly, to aid in identifying the species of mammal from which a given hair sample was obtained.