Although the observations concerning hairiness of body as an index of vigor, whether sexual or only generally physical, are so ancient, until recent years no attempts have been made to demonstrate on a large scale whether there is actually a correlation between hairiness and sexual or general development of the body. Some importance, therefore, attaches to Ammon's careful observations of many thousand conscripts in Baden. These observations fully justify this ancient belief, since they show that on the one hand the size of the testicles, and on the other hand girth of chest and stature, are correlated with hairiness of body. Ammon's observations were made on nearly 4000 conscripts of the age of 20. From the point of view of the hairy system he divided them, into four classes:-- I. To which 6.1 per cent, of the men belonged, with smooth bodies. II. Including 25.3 per cent., only slight hairiness. III. 53.8 per cent., more developed hairy system, but belly, breast and back smooth. IV. 14.7 per cent., hair all over body. V. 0.1 per cent., extreme cases of hairiness. The beardless were 12.1 per cent., those with no axillary hair 9 per cent., those with no hair on pubis 0.4 per cent. This corresponds with the fact that hair appears first on the pubis and last on the chin. In the first class 69 per cent, were beardless, 54 per cent, without any axillary hair and 6 per cent, without pubic hair. In the second class 24 per cent, were beardless, 17 per cent, without axillary hair. In the third class 3 per cent, were beardless and 3 per cent without axillary hair. Below puberty the diameter of testicles is below 14 millimeters. There were 13 conscripts having a testicular diameter of less than 14 millimeters. These infantile individuals all belonged to the first three classes and mostly to the first. The average testicular diameter in the first class was nearly 24 millimeters, and progressively rose in the succeeding classes to over 26 millimeters in the fourth. While there was not much difference in height, the first class was the shortest, the fourth the tallest. The fourth class also showed the greatest chest perimeter. The cephalic index of all classes was 84. (O. Ammon, "L'Infantilisme et le Feminisme au Conseil de Révision," _L'Anthropologie_, May-June, 1896.)