On the modes of measuring microscopic objects / by Harting of Utrecht.

Date:
[1852]
Catalogue details

Licence: Public Domain Mark

Credit: On the modes of measuring microscopic objects / by Harting of Utrecht. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    WUrijcU OX THE MODES OF MEASURING MICROSCOPIC OBJECTS. BY HARTING OF UTRECHT.1 [from the monthly journal of medical science for may 1852.] The determination of the size of objects seen through the microscope is, on various accounts, important. For when we examine bodies whose nature and distinctive characters are only revealed to us by properties appreciable by the sense of sight, every one of these properties becomes of consequence; and more especially does the determination of the dimensions of such bodies furnish some of their best specific characters,—being among the few which are totally inde- pendent of the subjective agency of the observer. Some have expressed the opinion, that very accurate measurements—at least in the case of objects from the organic kingdom, which vary greatly in size—are not requisite; and that it is sufficient to make an approximation, and express it by a number which, by its simplicity, may assist our conception regarding the size of the objects, without, at the same time, pretending to furnish the precise result of their actual and accurate measurements. This opinion, that micrometry is inapplicable to organic objects, is assuredly quite unfounded. It is true that of a hundred Negro skulls, or of a hundred European skulls, no two might be found of the same exact size ; and if both series were compared, skull by skull, it is very likely that some of the former might be discovered larger than some of the latter. But if the mean numbers, obtained from the sum of the dimensions of each series divided by 100, were compared, undoubtedly the mean of the first would be found to be smaller than the mean of the second series. This, then, would justify the general proposition, that a Negro has a smaller skull than a European. With the elementary parts, of which the organised tissues are composed, the case is similar. They all vary in size, but within certain limits which can be learnt; for if a sufficient number of measurements of these elementary parts be made, the mean result of each series expressed in numbers will constitute a cer- tain value, which, abstracting the probable amount of error inseparable from such results, may be regarded as a standard, furnishing one of the best specific char- acters for each object. In order that the mean shall be just, each separate measurement must be taken with exactitude; and this is especially necessary, when it is proposed to use these mean numbers as the foundation for observations on the progressive development of the different tissues at different periods of life. The best micrometric method is therefore that which gives the most accurate indications. But micrometry, like microscopic vision, has its limits, and the utmost that can be expected of any micrometric method is, that it shall put it in our power to attain results, in which the probable amount of error is less than the dimensions of the smallest object which can be seen through the microscope. We 1 Translated from Het Mikroskoop, vol. ii., p. 287, et seq. EDINBURGH : SUTHERLAND AND KNOX.