470 LEON AUGUSTUS HAUSMAN 
cating the extent of some of the cuticular scales. The disposi- 
tion of the colors shown indicated often the location and relative 
thickness of the various hair elements, and not infrequently 
caused the transverse edges of the cuticular scales to stand out 
prominently in black tracery against the background of some 
vividly contrasting color. The state of fusion of the cortical 
cells was often also indicated by the appearance of certain char- 
acteristic color associations. By arranging the hairs under 
examination at different angles on the slide and by including in 
one mount hairs of many different species, various beautifully . 
colored demonstrations of differences and similarities were ob- 
tained. It was found most satisfactory to mount hairs designed 
for polariscopic examination in some heavy oil (e.g., castor oil) 
or balsam. This treatment was, in fact, imperative for those 
hairs whose medullas were the objects of investigation. 
2. Preparation for the examination of the medulla. The meth- 
ods used to render the scales of hair prominent obscure the med- 
ulla. Consequently it was found necessary to devise some means 
of rendering the hair shaft transparent in order to bring the med- 
ullary cells or chambers into visibility. This was accomplished 
in the following ways: 
First method—clearing in water. This is the method of clari- 
fication commonly used for hairs of a not too great diameter in 
general. It works fairly well with the finer hairs which lack pig- 
ment in the cortex and whose cuticular scales are not closely set 
together, which is tantamount to saying that it works well with 
but very few. 
Second method—clearing in oils. It was found that clearing 
the hair in oils of various sorts, such as oil of bergamot, oil of cloves, 
oil of cedar, oil of origanum, and castor oil, tended to obscure 
almost entirely the markings of the scales and to make the hair 
shaft, in effect, a glassy cylinder, through which the medullary 
cells could be seen with great distinctness. The hair was first 
washed in the ether-aleohol solution as before, and then trans- 
ferred to a bath of oil, where it was allowed to remain for several 
minutes. It was then mounted in the same oil for microscopical 
examination. In the case of the larger hairs, it was often neces- 
