Sometimes a different method of representing the phenomenon graphically is followed, namely, by tracing the successive series of distances developed on the ordinates (Fig. 153); in which case the characteristic arrangement of the lines causes this to be known as the organ-pipe method.
Fig. 152.
Fig. 153.
The diagram for the growth in stature, given earlier in this volume, is constructed according to the method shown in Fig. 151. When there are a great number of data to represent, which overlap and interweave, this method of graphic representation still lends itself admirably to the purpose; in such a case we shall have a number of broken lines, either parallel or intersecting, which may be distinguished by different colours or different methods of tracing (dots, stars, etc.), so that they may interweave without becoming confused, thus giving us at a glance the development of several phenomena at once (for example, total stature and sitting stature, length of upper and lower limbs, in one and the same diagram).
For the purpose of practice, a graphic representation of the changes in ponderal weight through the different ages may be constructed in class. The figures for stature and weight at each age should be read aloud; one student can find the corresponding ponderal index in the tables, while another constructs the graphic line upon the blackboard.
In this manner we can see better than by reading the figures, how the ponderal index increases during the first year and becomes much higher during early infancy; and then how it diminishes up to the age of puberty, holding its ground with slight oscillations during the puberal period; after which it again increases when the individual begins to fill out after the seventeenth year, and once again later when he takes on flesh, to fall off again during the closing years, when old age brings lean and shrunken limbs.
Seriation.—Another method of rearranging the figures is that of seriation. Let us assume that we are taking the average of a thousand statures, or of hundreds of thousands. We will try to find some means of simplifying the calculation. Since the individual oscillations of stature are contained within a few centimetres and the individuals amount to thousands, large numbers will be found to have the same identical statures. Accordingly, let us rearrange the individuals according to their stature, obtaining the following result:
| Stature in metres | Number of individuals |
|---|---|
| 1.50 | 20 |
| 1.55 | 80 |
| 1.60 | 140 |
| 1.61 | 200 |
| 1.62 | 300 |
| 1.63 | 450 |
| 1.70 | 100 |
| 1.75 | 80 |
| 1.80 | 10 |