164 



THE AMEEICAK MONTHLY 



[September, 



had been matted together by blood 

 previous to its being heated, and was 

 able in that case to show that the hair 

 was from the head of an adult dark- 

 complexioned person. One of the 

 most important features developed 

 during this trial was the ability to 

 show that the blood in the meshes of 

 the hair was ante-mortem. 



' In cases of forensic microscopy 

 the importance of a careful exami- 

 nation of all minute fibres found upon 

 weapons cannot be too strongly in- 

 sisted upon. A case is related where 

 a razor was found which belonged to 

 a prisoner, on which were some small 

 fibres imbedded in blood, which, ex- 

 amined under a high magnifying 

 power, proved to be cotton. In cut- 

 ting the throat of his victim, the 

 murderer has also cut through the 

 cotton strings of her night-cap. The 

 similarity of the cotton fibres on the 

 razor belonging to the prisoner and 

 those of the strings on the deceased 

 woman's night-cap was fully estab- 

 lished. In another case, a knife 

 which had been used to inflict a fatal 

 w^ound, and vv^hich had been wiped 

 afterward, contained in its depres- 

 sions and irregularities, as well as 

 between the layers of the handles, 

 coagula of recent blood mixed with 

 rust. One remarkable circumstance 

 brought out by the microscope ap- 

 peared to connect the weapon with 

 the prisoner. In a small coagulum 

 found on the knife, dried and fixed to 

 the blade, were some woollen fibres 

 of a peculiar purple brown dye. 

 These corresponded exactly to the 

 fibres of the woollen jacket which the 

 prisoner wore. In examining hair 

 for the sole purpose of determining 

 whether it came from man or animal 

 we will find sufficiently characteristic 

 differences in that portion known as 

 the shaft, and we will, therefore, limit 

 our remarks to that part only, which, 

 in fact, is often the only portion of 

 the hair we are able to obtain in 

 medico-legal practice. The appear- 

 ance of the hair shaft varies consider- 

 ably in different persons, as it does 



also in the same person upon different 

 parts of the body ; but there is, never- 

 theless, the same general structure 

 which enables us to identify it with 

 little difficulty when under the mi- 

 croscope. Before entering upon the 

 distinguishing features of human from 

 animal hair, it will save repetition if 

 we first briefly refer to the general 

 structure of the hair shaft. 



' When we examine a hair, prop- 

 erly mounted under a low or medium 

 power, we can usually discern at once 

 its two principal anatomical parts, 

 the cortex and medulla. The me- 

 dulla, forming as it does a dark cen- 

 tral axis in the hair, gives it the 

 appearance of a tube — an illusion 

 which led some of the earlier observ- 

 ers into error. A thin transverse 

 section of the shaft at once corrects 

 this impression and shows the me- 

 dulla to be composed of cells of vari- 

 able size and shape. These cells 

 usually contain dark, coarse spots 

 which were at one time supposed to 

 be deposits of pigment, but have since 

 been shown to consist of air. This 

 can be easily demonstrated by allov\^- 

 ing a longitudinal section of hair to 

 soak in some volatile oil, when the 

 air will be displaced by the oil, and 

 the spots disappear and again reap- 

 pear upon evaporation of the oil. 

 The size and shape of these inedullary 

 air cells, as we shall see later on, 

 form one of the most noticeable dis- 

 tinctions between animal and human 

 hair. The linear portions or cortex, 

 which surrounds the medulla, is made 

 up of flat and generally nucleated 

 cells, the borders somewhat overlap- 

 ping each other. The minute anat- 

 omy of the cortex cannot be made out 

 without first subjecting the hair to 

 special preparation. By treating a 

 human hair, preferably a white one, 

 with caustic soda or potash, the cell 

 walls become plainly visible ; and, by 

 desiccation in wann nitric or sulphu- 

 ric acid, the individual cells may be 

 obtained, showing oftentimes with 

 beautiful distinctness their elongated 

 nuclei, and frequently in dark hair. 



