Fig. 145.—Method of measuring the total spread of arms.
Total Spread of the Arms.—This measurement is taken quite simply. The subject must place himself with his arms outstretched in a horizontal direction and on a level with his shoulders. The measurement corresponds to the distance intervening in a horizontal line from the tip of one middle finger to the other (Fig. 145). A specially constructed anthropometer may be used for this measurement. It has a long horizontal rod adjustable perpendicularly, so that it may be placed on a level with the shoulders of the subject to be measured. This rod forms a cross with the other vertical rod with which the subject should be in contact. The arms are then extended along the cross rod which is marked with a millimetric scale. But this greatly complicates the anthropometer, and hardly any anthropometer possesses this attachment. This measure may be successfully taken with the very simple aid of the wall. The only difficulty offered is that of securing a perfectly horizontal position for the arms. For this purpose horizontal lines, which either happen by chance to be upon the wall or which may be drawn on purpose, will be of assistance. In order to have guiding lines suited to different statures, several horizontal lines may be drawn intersecting the vertical line already traced for guidance of the millimetric tape measure used in taking the stature.
Thoracic Perimeter.—The thoracic perimeter is taken on the nude thorax, in an erect position and with the arms hanging beside the bust, by applying the millimetric measure in such a way that its upper margin passes just below the nipples. The tape measure should completely encircle the thorax in a horizontal plane passing through the mammary papillæ. Since the thorax is in constant motion, we must observe the oscillations of the tape measure and obtain the average; or else we may take the measurements during the state of expiration (repose). In giving the figure it is necessary to specify the procedure followed.
Vital Index. Index of Life.—Index of life is the name given to the proportion between the stature and the thoracic perimeter. It ought to be equal to 50, i.e., Tp = S/2
Vi = (100×Tp)/S = 50 (normal).
Weight.—The weight of an individual is taken by means of ordinary scales. In order to obtain the weight of the nude person, the clothing may be weighed separately and their weight subtracted from the total weight of the clothed person. The weight should be taken before eating, in order that unassimilated alimentary substances may not alter the real weight of the subject. If this method cannot be rigorously followed out, it should be specified how much clothing the subject retained, whether he had eaten, etc.
Ponderal Index.—Stature and weight are the most synthetic and comprehensive measurements of the form. But we need a clear proportion between these two measures to tell us whether an individual weighs more or less relatively to his stature. It may happen, for instance, that a stout person of short stature actually weighs less than another person who is tall and thin; but relatively to his stature he may on the contrary be heavier, that is, he may have a higher ponderal index. A robust and plump child will weigh in an absolute sense less than an adult who is extremely thin and emaciated; but relatively to the mass of his body he weighs more. Now this relative weight or index of weight (ponderal index) gives us precisely this idea of embonpoint, of the more or less flourishing state of nutrition in which an individual happens to be. But linear measurements such as the stature cannot be compared with volumetric measurements, such as the weight. Hence it is necessary to reduce the volumetric measure—the weight—to a linear measure, which is done by extracting the cube root from the number representing the weight. Then the root of the weight may be compared to the stature reduced to a scale of 100. By forming a general proportion, in which W represents the weight of a given individual, and S the corresponding figure of his stature, we obtain:
S:∛(W)::100:x (where x represents the ponderal index)
hence Pi = (100×∛(W))/S