THE MICROSCOPIC EXAMINATION OF SILK FIBRES. 57 
Preparation of the material for eramination.—As has already been in- 
timated, we were provided with no special apparatus for reeling the silk 
from the cocoons, and specimens for the measurement of the fineness 
and one set for determination of the tensile strength were obtained by 
simply cutting open the cocoons, separating the layers by pulling them 
apart, and taking portions of fibre at random from each part. No at- 
tempt was made to determine in this examination differences in the 
quality of the fibre dependent upon the location of the part in the strati- 
fication of the cocoon, and hence the period of the spinning operation at 
which it was formed, both because the time at our disposal for making 
the examination had been limited and because this did not constitute 
a principal object in the examination desired. There is no doubt, how- 
ever, that an investigation with this regard would furnish results of 
great interest and value. 
The fibres separated in this way were designated as “ dry ;” that is, uo 
moisture was employed in their separation. It is well known that the 
strength of the cocoon depends upon the glutinous character of the fibre 
on the instant of its issue from the spinnerets of the insect, and that the 
glutinous matter covering the fibre and forming a portion of its constit- 
uent structure readily softens in warm water. And it is further well 
known that this principle is applied practically in the industrial pro- 
cesses of silk reeling. To determine what influence this may have upon 
the fibre, we submitted a series of the cocoons to the action of warm 
water, and when they were sufficiently softened secured the end of the 
fibre and wound it upon slips of card-board, thus applying in a crude 
way the process of reeling. The fibre so obtained has therefore been 
designated as “ wet.” The influence of the treatment.to which the fibre 
is subject in this process of separating it will be discussed later on, and 
is manifest in the results given in Table II. 
Measurements of fineness.—If the fibre of raw silk be examined with a 
microscope of sufficiently high power, it appears to consist of a more 
or less flattened strip, somewhat depressed through the middle, so that 
its cross-section may be likened to the longitudinal section of a dumb- 
bell (co), as shown in the figure. Thisis explained by the fact that the 
fibre in the glutinous condition is discharged by the worm in spinning, 
from the spinnerets located on the under side of the head, near the man- 
dibles. As they pass out and are stretched by the worm in its to-and- 
fro motions in spinning, the two fibres are cemented together more or 
less firmly according to the rapidity of spinning. 
Sometimes these primary fibres, as they may be termed, are separate 
and free from each other, and each is an almost perfect elongated cylin- 
der. But in most cases they are firmly joined, and the two form a 
compact whole, constituting the raw fibre of the.cocoon. It is plain, 
therefore, that this raw fibre is not cylindrical but ribbon-shaped, and 
that it has two lateral axes of different lengths, so that on some accounts 
a single measurement of a fibre does not represent its fineness, while at 
