85rO Hoijal Soeieii/, 



daring the last two years. There is no similar alteration of struc- 

 ture of the eyebrows and eyelashes. His complexion is dark, while 

 that of a younger brother is fair ; and the latter is free from any 

 alteration of the hair. 



Examination of the hair with a lens shows that the cylinder of 

 the hair is perfectly uniform, that the white portion is contained 

 within the cuticle and occupies the whole breadth of the cylinder ; 

 whilst it frequently presents a rounded cone at the central extremity, 

 and breaks up into tibres at tiie opposite or distal end ; and in some 

 instances this fibrous structure is apparent at both ends of the white 

 segment. Moreover, by transmitted light, the white segment is 

 found to be opake, and consequently presents a dark shade, while 

 the intermediate or brown portion has the transparency of normal hair. 



When the transparency of the hair is increased by immersion in 

 Canada balsam slightly diluted with spirits of turpentine, the white 

 and opake segment is reduced in dimensions, and is rendered more 

 or less transparent by imbibition of the volatile fluid ; moreover it is 

 clearly demonstrated by this process that the opacity of the segment, 

 its whiteness when seen by reflected light, and its darkness by trans- 

 mitted light are all due to the presence, in the fibrous portion of the 

 hair, of spaces filled with air-globules. The air-spaces are neces- 

 sarily very numerous and assembled closely together ; while at the 

 ends of the white segment they have more or less of a linear arrange- 

 ment, and give a fibrous appearance to the opake mass. More- 

 over the partial transparency of the hair caused by the balsam 

 demonstrates that, besides the air-spaces, large and small, contained 

 in the opake portion, minute air-spaces, sometimes arranged in linear 

 order, and sometimes communicating and forming short irregular 

 canals, are also met with in the transparent part of the hair. And, 

 in addition to the minute air-spaces of the plates of the fibrous por- 

 tion of the hair, an accumulation of air- globules is also very apparent 

 in the cells of the medulla. 



It is evident, from this examination of the hairs, that they are im- 

 perfect in structure and development, and that their imperfection 

 indicates a weak producing organ, and probably a weakly constitution 

 of the individual — that the cells of which the fibrous portion of the 

 hair is composed, instead of being filled with a horny plasma, are 

 turgid with aqueous fluid, and the desiccation of this fluid leaves 

 behind it vacuities which in the subsequent growth of the shaft be- 

 come filled with air. The most remarkable phenomenon in connexion 

 with the case, however, is the alternation of imperfect and perfect 

 cells, the period of continuance of the two processes (supposing 

 them to be equally active in point of time) being twice as long for 

 the perfect as for the imperfect structure. 



Since the publication of the observations of Berthold in Miiller's 

 *Archiv' for 1850, it is generally beheved that the hair grows faster 

 during the day than during the night ; hence the first suggestion 

 that occurred to me in connexion with the present case, seemg that 

 the white or opake segment was shorter by one-half than the brown, 

 was that the former represented the slower growth by night, and 

 the latter the quicker growth by day — the white and the brown 



