Microscopic Structure of the Wool Fiber

Abstract

An investigation was undertaken to obtain information con cerning the fine details of structure of wool fibers and especially of their constituent scale and cortical cells. Treatment of chemi cally modified wool with the enzyme, pepsin, was found to be an excellent method for releasing individual cells for such studies. It is shown by microdissection that the striated appearance of the cortical cells is due to the presence of many fibrils which can be separated with microneedles. Near the center of each cell is a nucleus which has a granular structure. Between crossed nicols, the fibrillar part of the cortical cells appears birefringent, whereas the nucleus does not. The scales show little internal organization such as exhibited by the cortical cells. When examined with crossed nicols they appear nonbirefringent. Unlike the cells of the cortex, the scales are not easily separated by treatment with enzymes, but remain attached to each other in a manner comparable to the arrangement of shingles on a roof. A comparison of root and shaft of the fiber reveals numerous differences in reaction to microchemical color tests, as well as differences in cellular structure. The root, for example, gives a positive test for sulfhydryl groups whereas the shaft gives a nega tive test. Similarly, the shaft appears birefringent whereas the root does not. These and other observations clearly indicate that as the cells of the root emerge into the shaft a number of physical and chemical changes take place simultaneously. When wool is placed in chlorine water bubbles arise on the surface of the fibers (Allwörden reaction). Evidence is presented in support of the viewpoint that these bubbles arise solely from the scales and that their formation is associated with the reaction of the chlorine with disulfide groups of the cystine in the scales.