full dimensions until a rather late period in life, they will have tended, in accordance with the law often indicated, to transmit their characters to their male offspring alone; and thus the great inequality in size between the sexes of the Scotch deerhound may probably be accounted for. [Illustration: Fig. 63. Head of common wild boar, in prime of life (from Brehm).] The males of some few quadrupeds possess organs or parts developed solely as a means of defence against the attacks of other males. Some kinds of deer use, as we have seen, the upper branches of their horns chiefly or exclusively for defending themselves; and the Oryx antelope, as I am informed by Mr. Bartlett, fences most skilfully with his long, gently curved horns; but these are likewise used as organs of offence. Rhinoceroses, as the same observer remarks, in fighting parry each other’s sidelong blows with their horns, which loudly clatter together, as do the tusks of boars. Although wild boars fight desperately together, they seldom, according to Brehm, receive fatal blows, as these fall on each other’s tusks, or on the layer of gristly skin covering the shoulder, which the German hunters call the shield; and here we have a part specially modified for defence. With boars in the prime of life (see fig. 63) the tusks in the lower jaw are used for fighting but they become in old age, as Brehm states, so much curved inwards and upwards, over the snout, that they can no longer be thus used. They may, however, still continue to serve, and even in a still more effective manner, as a means of defence. In compensation for the loss of the lower tusks as weapons of offence, those in the upper jaw, which always project a little laterally, increase so much in length during old age, and curve so much upwards, that they can be used as a means of attack. Nevertheless an old boar is not so dangerous to man as one at the age of six or seven years.[322] [Illustration: Fig 64. Skull of the Babirusa Pig (from Wallace’s ‘Malay Archipelago’)]