Physiological histology, methods and theory / by Gustav Mann.

Gustav Mann

Date:: 1902

Credit: Physiological histology, methods and theory / by Gustav Mann. Source: Wellcome Collection.

28/524 page 6

$of functional activity, such as division and secretion, or while absorbing food. If we have ascertained by an exact study of the most diverse fixatives that they all agree in producing in the cells under investi¬ gation certain effects in common—for example, a definite number of chromatin segments—we have every right to suppose that the common feature is the outcome of something which was preformed in the living cell, but which for optical reasons we could not discern as long as life lasted. Now an entirely new question arises, namely, to what extent is a cell-organ, revealed by different methods, preserved in its original state ? By what changes in its physical or chemical composition does it become visible ? In respect of gross external characters, as maintenance of shape or mutual arrangement of cell-organs, it is not difficult to come to a conclusion ; for example, alcohol—wTiich shows chromatin segments as do other fixatives—distorts them by its diffusion cur¬ rents ; other reagents, again, by their slow action, do not fix all the cell-contents simultaneously, in consequence of which a general dis¬ arrangement becomes evident as compared with similar cells fixed by quickly acting solutions. Further, some reagents, because of dif¬ ferences in their general precipitating power, show certain structures attenuated and shrivelled, which after the use of other fixatives appear in a more bulky and denser form. Which amongst these varied appearances are we to choose as the one nearest to nature ? The one which suits our fancy most, either because of its shape or its colour reactions ? I think not. Let each cell-organ be examined in a systematic way, not by one but many reagents; do not describe only the effects produced by what some call the best fixative, leaving out the effects produced by ‘ bad ’ ones ; give other investigators the benefit of ‘failures,’ and thus gradually help to build up a systematic way of investigating cells. Only after a complete and separate investigation of the cell-body and the nucleus, by fixatives especially suited to each of them, is it permissible for purposes of reconstruction to combine into one scheme those features which were obtained repeatedly by diverse means \ Some people, on reading Hardy’s results, may think, If coagulation always produces a foam or net-like structure in colloidal homogeneous substances, what right have we to make deductions as to the original condition of cells ? To me it seems that such a person is assuming in the first instance that the structures just mentioned are always produced, and in the second instance that the substances under investigation, and also the cell, are homogeneous. Hardy himself has stated that the surfaces of conjugate fluids and the advancing edge of a white of egg solution do not show a net-like arrangement, and reference to my slide and test-tube experiments (p. I25)will further show that absolutelyuniform, granular membranes 1 Following this plan, I have during the last five years employed close on 200 distinct fixing methods on nerve-cells.$

Physiological histology, methods and theory / by Gustav Mann.

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