Page:Science vol. 5.djvu/318

294 The experiments which we have been considering compare favorably as to methods and care with previous experiments of the same sort: and it does not seem unwarranted to conclude that those, also, are subject to errors of somewhat the same magnitude. It appears plain that we can, with proper care, determine the digestibility of the total ration fed with a very satisfactory degree of accuracy; but it seems equally plain that we cannot compute from that result the digestibility of any single fodder composing the ration with the hope of obtaining any thing more than approximately correct figures. The data which we have for the digestibility of the concentrated fodders are of more or less value for practical purposes, since they are usually the average of several determinations; but for scientific purposes such determinations are of very doubtful value.

the February number of the Journal of the Anthropological Institute of Great Britain and Ireland, Mr. Francis Galton describes the laboratory which he established at the International health exhibition to familiarize the public with simple methods of measuring and recording many of the physical characteristics of man. The instruments in action dealt with keenness of sight, color-sense, judgment of eye, hearing, highest audible note, breathing-power, strength of pull and squeeze, swiftness of blow, span of arms, height standing and sitting, and weight. Some other apparatus not in actual use, such as a balance to determine delicacy of touch, was exhibited.

All these instruments were so contrived as to economize the time of the attendant; so that, although each person measured was in the laboratory about twenty minutes, he consumed but seven minutes of the attendant's time. Thus it was possible to measure ninety persons daily, and cover the running expenses of the laboratory with a tax of threepence each. Of course, the reduction of expense to a minimum gives a much broader field for work, especially in introducing periodic systematic measurements into schools, which is one of the ultimate objects of this demonstration.

Keenness of sight, or power of accommodation of the eye, was measured by means of an original instrument of a flat, sickle-shape, upon which were set upright, at regular intervals, small blocks of wood, covered below with printing in diamond type, and having printed at the top in large type the distance in inches from the eye-piece. The number of inches at which the diamond-type is legible is an expression of the accommodating power. This test showed, that, of 850 persons, forty per cent had both eyes equally effective, while sixty per cent had a notable difference in the power of the two eyes. The average difference between the two eyes was two inches; but the average strength of the right and left eye was almost exactly the same. The color-test was Holmgren's light-green test, nicely arranged to economise time. Judgment of the eye in dividing a line into halves, and in setting a movable arm square upon a board, were tested in ingenious ways, which doubtless among children would express the native quality, but oftentimes among adults would be only a measure of facility acquired by occupation, The highest audible note was measured by five whistles, set to emit 10,000, 20,000, 30,000, 40,000, and 50,000 vibrations per second respectively. Of 317 males between forty and fifty years of age, a hundred per cent heard the first whistle, to four per cent who heard the last. In this, as in every other particular, the males excel the females.

The spirometer used consists of a counterpoised vessel suspended in water, which rises as air is breathed into it, and shows the number of cubic inches of displacement by a scale at its side. The breathing-capacity increases rapidly in early youth, becomes stationary between twenty and thirty, or a little later, and thenceforward steadily declines. Up to the age of twenty, the breathing-capacity has been the same for both sexes; but at that age that of the males becomes half as great again,—a ratio which is maintained throughout after-life. Unexpectedly, it appears that there is no close relation between the breathing-capacity and the strength of pull or of squeeze. The latter, which were estimated by means of Salter's instruments for the purpose, show that the left hand is about six per cent weaker than the right, and that women are weaker than men. Of the 1,657 adult women measured at the laboratory, the strongest could exert a strength of squeeze of but eighty-six pounds, or about that of an average man.

For the first time, swiftness of blow was measured, either of a blow delivered with the flat straight at a pad upon one end of a flat bar running freely between guides, or of a pull, by holding a stirrup attached by a string to a similar bar, and striking out into space. The swiftness is registered by means of a spring with pencil attached, which is set free, and vibrates transversely as soon as the bar begins to move. The results of this measurement are not discussed.

A curious fact, which came to light on comparing the height sitting with the height standing, is, that in women an increase in stature is accompanied by a disproportionate increase in the length of the legs, while in men, for all statures up to six feet, the ratio between height sitting and height standing is the same, 54:100.

During the continuance of the laboratory, 9,827 persons were measured, of whom 4,726 were adult males, and 1,657 were adult females. The results of all these measurements are not fully discussed, nor has Mr. Gallon perfected his ideal of a laboratory. Among other measurements which will be added to the list, are those of the head, its maximum length and breadth with graduated calipers, and its