Repository: UIHistories Project: Board of Trustees Minutes - 1886 [PAGE 233]

EXTRACTED TEXT FROM PAGE:

225 To diminish the transparency of the fibre it is often desirable to submit it to the action of analine or other dyes. I have used with very great advantage a weak solution of silver nitrate in ammonia. The wool is digested in this solution a few minutes, then taken out, washed, dried, and gently warmed for some time. It quickly turns drab, and renders the fibre much more opaqae. Bat in the use of this substance, great care must be observed not to make it too strong, because then the fibres may be made too black. Upon the whole, however, I think that, with suitable mounting media, staining may be avoided. If, now, when the wool is thus prepared and mounted for examination, it be brought within the focus of a good microscope, its external characteristics become manifest. It is presented to the vision as a broad band with nearly parallel edges, the latter sometimes provided with slight projections, often erroneously called serrations, while the surface is covered transversely with irregular lines. And wTe find, too, that some of these lines are connected with the serrations seen at the edge of the image. The fibre is generally transparent in white wools, opaque in colored wools, while some of the long wools exhibit through the middle of the image a portion much less transparent than the remainder, indicating a difference in the structure in that portion. It is important to observe in this connection that a perfectly neutral substance should be used for the mounting medium or the fibre will become distorted and in time disintegrated. But if the fibre be placed for examination in some tolerably strong caustic alkali or acid the fibre swells and the transverse lines already mentioned become more marked, ultimately showing that they represent the edges of scale-like appendages or coverings which, by longer continued action and with the aid of heat, may be completely separated. With care in manipulation it wrill appear that these scales, which are infinitely thin, are attached to an equally thin membrane or skin surrounding the fibre. If sulphuric acid (oil of vitriol), not too strong, be used to produce the disintegration, and during the operation slight abrasion be applied by pressure upon the <jover glass, and careful movement, this skin with the scales attached will slip away from the body of the fibre and may be studied separately. It is found upon all wools, but may be obtained separately more readily from the down wools than from the others. The scales upon the wools of different breeds appear to have a more or less characteristic form, and it has been believed that the forms manifested could be made a basis of differentiation of breeds. I t appears, however, that more study in this line will be needed, and that even if it can be applied, long practice in examination will be needed to detect impurities of blood in this way. At the same time there is no doubt of the value of the indications sometimes afforded. In the long wools the scales are more or less angular, the edges broken, and the general form irregular, especially in the coarser fibres. In the short and medium wools greater regularity prevails; the edges are more definitely curved and have more tendency to extend around the fibre, while at the same time they are more Ind—15