1884.] 



MICROSCOPICAL JOURNAL. 



165 



pigment markings. The cortex of a 

 human hair, especially, is hard, 

 tough, and yet elastic. This permits 

 of brushing, combing, and of even 

 much rougher treatment "without in- 

 jury to its normally smooth contour. 

 We would remark, in passing, that 

 this is a point of some value in fo- 

 rensic microscopy, as we frequently 

 find dents, of more or less depth, in 

 hair taken from vs^eapons which have 

 been used in assaults. Such dents 

 or other injuries to the cortex, when 

 observed in hair remaining on the 

 victim's head, may lead to a pi"esump- 

 tion as to the kind of weapon used. 



' With these remarks v^e may now 

 inquire into the characteristic distinc- 

 dons which exist between human hair 

 and animal hair. For the purpose 

 of convenience they may be consid- 

 ered under the following heads, viz : 

 First, The relative proportions of the 

 cortical and medullary structures. 

 Second, The size, shape, and arrange- 

 ment of the medullary cells. Third, 

 The size, shape, and arrangement of 

 the superficial cortical cells. Fourth, 

 The size and shape of the hair shaft. 



' First, the relative proportion of the 

 cortical and medullary structures. In 

 animals, the medulla almost always 

 forms a much larger proportion of 

 the hair shaft than in man, though 

 there are a number of exceptions to 

 this general rule. In hair from cer- 

 tain quadrumana, the monkey for 

 example, the relative proportion of 

 medulla is about the same as in the 

 hair from man, though its appear- 

 ance is different. The stronger and 

 denser the hair, the greater is the 

 thickness of the cortical structure, 

 while, conversely, the lighter, more 

 pliable, and spongy the hair the 

 greater is the proportion of the me- 

 dulla. This rule is well illustrated 

 in such typical examples as the pig's 

 bristle, intended more for protection 

 than warmth, with its hard, horny 

 cortex and proportionally small me- 

 dulla, and on the other hand the soft, 

 pliable, though coarse hair of the 

 deer, with its thin delicate cortex and 



full spongy medulla, evidently con- 

 structed as much for warmth as pro- 

 tection from violence. So universal 

 is this rule that, with a full knowledge 

 of the life history of a given animal, 

 we can form an opinion as to the 

 relative proportion of cortical and 

 medullary structures with consider- 

 able accuracy, even before we have 

 made a microscopic observation. 



' Second, size, shape, and arrange- 

 ment of medullary cells. In human 

 hair we find the medullary cells of 

 variable size, irregularly round, that 

 is, in such diverse shapes as globu- 

 lar cells assume when in close and 

 crowded aggregations. They differ 

 in general appearance from the cor- 

 responding cells in most hairs of 

 animal oi-igin. They are smaller, 

 more crowded, and unless specially 

 prepared, less distinct than the me- 

 dullary cells in animal hairs of the 

 same diameter. In hair from most 

 of our domestic animals we find the 

 size, shape, and arrangement of these 

 cells to be so totally unlike those in 

 human hair as to be contradistin- 

 guished at a glance when properly 

 mounted and viewed under a good 

 glass by transmitted light. In the 

 rodentia, for example, these cells are 

 mostly arranged in pretty regularly 

 longitudinal lines, the medulla in the 

 finest hairs being composed of but a 

 single row of more or less distinctly 

 separated cells. 



' Third, the size, shape, and arrange- 

 ment of the superficial cortical cells. 

 In human hair these are thin, flat, and 

 usually fusiform, superimposed flatly 

 one on another, and overlapping so as 

 to give the appearance of very fine 

 in^egular transverse striae on the sur- 

 face of the hair, and a delicate ser- 

 i-ated edge on the outer borders. The 

 projection of these superficial cortical 

 cells is only equal to the thickness of a 

 single cell. On the other hand, in ani- 

 mal hair, where the cortex at all re- 

 sembles that of human, the striae are 

 coarser, more distinct, the lines more 

 widely separated and the edges gen- 

 erally more deeply serrated. In many 



