The microscope and its revelations . ure of the Human hair is in certain re-spects peculiar. When its outer surface is examined, it is seento be traversed by uTcgular lines (Fig. 312, a), which are moststrongly marked in fcetal hairs ; and these are the indicationsof the imbricated arrangement of the flattened cells or scaleswhich form the cortical layer. This layer, as is shown bytransverse sections (c, d), is a very thin and transparentcylinder; and it incloses the peculiar fibrous substance, thatconstitutes the principal part of the shaft of the hair. Theconstituent fibres of this substance
The microscope and its revelations . ure of the Human hair is in certain re-spects peculiar. When its outer surface is examined, it is seento be traversed by uTcgular lines (Fig. 312, a), which are moststrongly marked in fcetal hairs ; and these are the indicationsof the imbricated arrangement of the flattened cells or scaleswhich form the cortical layer. This layer, as is shown bytransverse sections (c, d), is a very thin and transparentcylinder; and it incloses the peculiar fibrous substance, thatconstitutes the principal part of the shaft of the hair. Theconstituent fibres of this substance, which are marked-out bythe delicate strise that may be traced in longitudinal sectionsof the hair (b), may be separated from each other by crushingthe hair, especially after it has been macerated for some timein sulphuric acid; and each of them, when completely sepa- STEUCTUKE OP HAIES. 701 rated from its fello^s, is found to be a long spindle-shaped the axis of this fibrous cylinder^ there is very commonly a Fr&. U^:.:,.:... ,:.:;:;.„, :.,:::ii^ Structm-e of Suman Hair:—a, external surface of the shaft,showing the transverse strife and jagged boundary caused by the im-brications of the cortical substance; b, longitudinal section of theshaft, showing the fibrous character of the medullary substance, andthe aiTangement of the pigmentary matter; c, transverse section,showing the distinction between tlie transparent envelope, the cylinderof medullary substance, and the cellular centre; d, another transversesection showing deficiency of central cellular substance. band which is formed of spheroidal cells ; but this is usuallydeficient in the fine hairs scattered over the general surface ofthe body, and is not always present in those of the head.*The hue of the hair is due, partly to the presence of pig-mentary granules, either collected into patches, or diffusedthrough its substance; but partly also to the existence of amultitude of minute air-spaces, which caus
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Keywords: ., bookcentury1800, booksubjectmicroscopes, booksubjectmicroscopy
