468 LEON AUGUSTUS HAUSMAN 
structed as follows: Upon a glass slide were fastened with Canada 
balsam two small corks, of firm texture, transpierced by fine cop- 
per wires, with their opposite ends bent into loops. Between the 
inner loops of these wires and between the corks, the hair under 
study was stretched and fastened at each end with droplets of 
balsam or viscous mucilage. The copper wires were now drawn 
out carefully away from one another until the hair between them 
was stretched taut, and the whole device placed upon the stage 
of the microscope. By gently tapping the outer loops of the 
copper wires with a dissecting needle, the hair could be with the 
greatest delicacy turned in either direction while under examina- 
tion. It was discovered that a small drop of a 25 per cent aque- 
ous solution of caustic soda or potash placed near one extremity 
of the stretched hair softened this portion to such an extent that 
the hair could be more easily rotated by turning but one of the 
copper wire loops. Not only could the hair be rotated, but also 
stretched slightly, and this was an advantage often, inasmuch as 
the lengthening of the cortex slightly separated the cuticular 
scales and rendered the depressions between them a trifle deeper. 
This device proved equally useful also in the examination of 
the medulla. The hair was first washed in the ordinary way, as 
has been described, and then cleared in clove or cedar oil, after 
which it was dried between two pieces of lens paper and stretched 
in the hair rotator as previously described. The configuration 
of the medullary cells and the relation of individual and groups 
of cells to each other was by this means brought out in the most 
satisfactory manner. Several of the hairs were, after having 
been cleared in xylene, allowed to remain in a bath of balsam for 
several hours, and then taken out, hung up like candles, and 
allowed to dry covered with a thin film of hardening balsam. 
These were then mounted in the hair rotator, and thus a com- 
pletely balsam-mounted hair secured for examination. It was 
found, however, that in the main this precedure gave no more 
satisfactory results than simply clearing in clove or cedar oil 
before mounting in the rotator, though there were instances in 
the cases of some of the larger hairs in which it was thought that 
the clearing in xylene insured a slightly greater clarification of 
