. The microscope and its revelations. FIG. 764.—Structure of human hair : A, external surface of the shaft, show-ing the transverse strife and jagged boundary caused by the imbrications ofthe cuticular layer; B, longitudinal section of the shaft, showing thefibrous character of the cortical substance, and the arrangement of thepigmentary matter; C, transverse section, showing the distinction be-tween the cuticular envelope, the cylinder of cortical substance, and themedullary centre; D, another transverse section, showing deficiency ofthe central cellular substance. (•ells ; but this ; medulla
. The microscope and its revelations. FIG. 764.—Structure of human hair : A, external surface of the shaft, show-ing the transverse strife and jagged boundary caused by the imbrications ofthe cuticular layer; B, longitudinal section of the shaft, showing thefibrous character of the cortical substance, and the arrangement of thepigmentary matter; C, transverse section, showing the distinction be-tween the cuticular envelope, the cylinder of cortical substance, and themedullary centre; D, another transverse section, showing deficiency ofthe central cellular substance. (•ells ; but this ; medullary substance is usually deficient in the finehairs scattered over the general surface of the body, and is notalways present in those of the head. The hue of the hair is duepartly to the presence of pigmentary granules, either collected intopatches or diffused through its substance, but partly also to theexistence of a multitude of minute air-spaces, which cause it to IO32 VERTEBBATED ANIMALS appear dark by transmitted and white b
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
