186 Proceedings of the Royal Physical Society. 
apparent variety and beautiful cellular structure. Plucking 
a few at random from the upper surface of the body, I found 
I had got three different varieties : large flattened hairs, 
showing a combined series of cells ; smaller hairs, containing 
a single series of cells ; and each displaying the external or 
epithelial coating of the hair, which forms a series of over- 
lapping margins or scales, their free edges being directed to- 
wards the points of the hair ; and, lastly, small bent or curved 
solid horny-like hairs, with this overlapping external coating 
developed here and there into large hook-like processes or spines. 
At my request, my friend Dr T. Strethill Wright made a 
minute microscopical examination of these hairs, and sketched 
the accompanying careful drawings (see Plate VIII.), which 
show very well their beautiful structure. Dr Wright used 
simply water in examining some of the hair ; and this fluid 
entering by the cut extremities, and permeating the hair 
thoroughly, distinctly revived and exhibited their internal 
cell structure. In the smaller-sized hair, containing only 
one series of cells, the cells are found to have an hour- 
glass contraction in the middle, the lower half of the cell con- 
taining the colouring-matter of the hair, and the upper part of 
the cell displaying a distinct central nucleus, the existence of 
which, at least in the body of tlie hair, is a fact which was new 
to both of us, if not altogether new to microscopists in general 1 
These nuclei were also beautifully seen in the cells of the 
larger hairs. Dr Wright has figured (Plate VIIL fig. 4) 
the peculiar appearance which some of the hairs displayed, of 
black bars, arranged in a somewhat parallel manner, or zig- 
zagging from one extremity to the other, in the central 
portions of the bodies of the hair ; for the lower, and upper 
portions of all the hairs, showed no cell cavities, being formed 
apparently of solid structure. These black bands were due to 
some of the uncut hairs being mounted in turpentine or balsam, 
which did not permeate the hair like the water, but obscured 
their true structure altogether, by enclosing the air as a black 
band, which was varied both in shape and in contiguity, in 
the lacerated cells of the hair. 
Thick hair or fur of a cellular structure containing thus 
enclosed a considerable amount of atmospheric air, a bad con- 
ductor of heat, and therefore useful in preventing the rapid 
