THE CHARTS. 



The charts, which, with only two exceptions, treat "of disease, are derived from 

 Tables 16, 17, 18, 19, 20, and 22, and have been prejDared for the pm-pose of picturing 

 to the eye the most interesting results of the tables by assembling isolated statements 

 and representing numbers by lines or bars which bear the same relation, in linear 

 measurement, to each other as do the numbers for which thev stand. 



Much elaboration in describing the plan adopted would be superfluous ; but. it may 

 be stated as a recognized fact, that, as conclusions which the mental faculties draw by 

 aid of the sight per se are instantaneous and without effort, the mind througli this 

 medium is capable of receiving manifold impressions at the same time, and of simul- 

 taneously comparing- many elements. If, for example, ten lines erected from the same 

 base, but of various lengths, be presented to the eye, the mind instantly compares each 

 with the others, determining without effort the longest or the shortest, etc.; but if in 

 their stead ten abstract numbers, having relatively to each other the same value as the 

 lines, be presented, although the medium of communication with the brain is in both 

 cases the same, each has to be observed and its value determined by a certain mental 

 process before a comparison can even be instituted. A landscape may be voluminously 

 and even completely described, so far as words are adequate, but one glance at a paint- 

 ing of the scene will convey more satisfactory knowledge. The manner of presenting 

 some of the facts herein set forth by charts is intermediate between the description 

 and the painting, but very little study wjll enable the reader to see clearly that which 

 is obscure when presented in another way, and to form conclusions which must be 

 laboriously extracted from statistics in their usual form. 



For convenience of reference and a proj^er division of subjects, the charts have been 

 divided into four classes, designated numerically. Those which compose Class I show 

 the relation of various diseases to social condition, complexion, age, height, and 

 nativity ; those of Class II show the relation of diseases to occupation ; those of Class 

 III show the relation to locality, (by States ;) and Class IV, consisting of only two 

 charts, shows the relation of both height and girth of chest to age and nativity In each 

 cliart, two columns of figures are given — the first showing the number of men examined 

 of each particular height, age, nativity, etc., or in each State, or of each occupation ; 

 the second giving, not the number, but tlie millesimal ratio rejected. Elsewhere, the 

 importance of the ratios is dwelt upon ; but it may not be supererogatory to caution the 

 reader that in forming his conclusions as to the prevalence of a disease, he has to deal 

 with ratios, and not with the actual number of men rejected. To the student of 

 anthropology this caution is unnecessary, but it is by no means infrequently the case 



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