There is no thorough and comprehensive modern study of the penis on an anthropological basis (though I should mention a valuable and fully illustrated study of anthropological and pathological variations of the penis in a series of articles by Marandon de Montyel, "Des Anomalies des Organs Génitaux Externes Chez les Aliénées," etc., _Archives d'Anthropologie Criminelle_, 1895), and it would be out of place here to attempt to collect the scattered notices regarding racial and other variations. It may suffice to note some of the evidence showing that such variations seem to be numerous and important. The Arab penis (according to Kocher) is slender and long (a third longer than the average European penis) and with a club-shaped glans. It undergoes little change when it enters the erect state. The clothes leaves it quite free, and the Arab practices manual excitement at an early age to favor its development. Among the Fuegians, also, according to Hyades and Deniker (_Cap Horn_, vol. vii, p. 153), the average length of the penis is 77 millimeters, which is longer than in Europeans. In men of black race, also, the penis is decidedly large. Thus Sir H.H. Johnston (_British Central Africa_, p. 399) states this to be a universal rule. Among the Wankenda of Northern Nyassa, for instance, he remarks that, while the body is of medium size, the penis is generally large. He gives the usual length as about six inches, reaching nine or ten in erection. The prepuce, it is added, is often very long, and circumcision is practiced by many tribes. Among the American negroes Hrdlicka has found, also (_Proceedings American Association for the Advancement of Science_, vol. xlvii, p. 475), that the penis in black boys is larger than in white boys. The passages cited above suggest the question whether the penis becomes larger by exercise of its generative functions. Most old authors assert that frequent erection makes the penis large and long (Schurig, _Spermatologia_, p. 107). Galen noted that in singers and athletes, who were chaste in order to preserve their strength, the sexual parts were small and rugrose, like those of old men, and that exercise of the organs from youth develops them; Roubaud, quoting this observation (_Traité de l'Impuissance_, p. 373), agrees with the statement. It seems probable that there is an element of truth in this ancient belief. At the same time it must be remembered that the penis is only to small extent a muscular organ, and that the increase of size produced by frequent congestion of erectile tissues cannot be either rapid or pronounced. Variations in the size of the sexual organs are probably on the whole mainly inherited, though it is impossible to speak decisively on this point until more systematic observations become customary.