FOUR FIGURES
The important researches of Held ( , 1897) ) on the structure of the nerve cell, those of A. Fischer (1899) on the fixation, staining and structure of protoplasm, of Butschli (1892) on protoplasmic foams, and of Hardy (1899) on the structure of gels, marked a new epoch in the history of cytological research.
From a study of the surviving nerve cells from various sources and a comparison of the results so obtained with the appearances of nerve cells in fixed preparations treated in various ways, Held came to the conclusion that the familiar Nissl bodies of the nerve cell were not present as such in the living cell but on the contrary were products of a precipitation, by the reagents, of a substance which existed in the living cell in a state of solution diffused through the cytoplasm.
A. Fischer (1899), in an extensive study of the effect of commonly used histological fixing agents on protein solutions of various compositions, showed that by the action of these reagents sponge-like, filamentous and granular structures could be produced in otherwise homogeneous solutions.
Hardy (1899) showed that gels fixed under tension presented along the lines of stress filamentous structures resem-'The authors are indebted for aid in these investigations t o a grant from the Chemical Foundation, including a Julius Stieglitz Fellowship in Chemistry Applied t o Medicine awarded to one of us (Gersh). They were also aided by a grant to The University of Chicago by the Rockefeller Foundation.
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