These variations in the number or structure of the mammary apparatus (_mammarium_) have become doubly interesting in the light of recent research in comparative anatomy. It has been shown that in man and the apes we often find redundant mammary glands (_hyper-mastism_) and corresponding teats (_hyper-thelism_) in both sexes. Fig. 103 shows four cases of this kind—_A, B,_ and _C_ of three women, and _D_ of a man. They prove that all the above-mentioned numbers may be found occasionally in man. Fig. 103 _A_ shows the breast of a Berlin woman who had had children seventeen times, and who has a pair of small accessory breasts (with two nipples on the left one) above the two normal breasts; this is a common occurrence, and the small soft pad above the breast is not infrequently represented in ancient statues of Venus. In Fig. 103 _C_ we have the same phenomenon in a Japanese girl of nineteen, who has two nipples on each breast besides (three pairs altogether). Fig. 103 _D_ is a man of twenty-two with four pairs of nipples (as in the dog), a small pair above and two small pairs beneath the large normal teats. The maximum number of five pairs (as in the sow and hedgehog) was found in a Polish servant of twenty-two who had had several children; milk was given by each nipple; there were three pairs of redundant nipples above and one pair underneath the normal and very large breasts (Fig. 103 _B_). A number of recent investigations (especially among recruits) have shown that these things are not uncommon in the male as well as the female sex. They can only be explained by evolution, which attributes them to atavism and latent heredity. The earlier ancestors of all the primates (including man) were lower placentals, which had, like the hedgehog (one of the oldest forms of the living placentals), several mammary glands (five or more pairs) in the abdominal skin. In the apes and man only a couple of them are normally developed, but from time to time we get a development of the atrophied structures. Special notice should be taken of the arrangement of these accessory mammæ; they form, as is clearly seen in Fig. 103 _B_ and _D,_ two long rows, which diverge forward (towards the arm-pit), and converge behind in the middle line (towards the loins). The milk-glands of the polymastic lower placentals are arranged in similar lines.