konGl. sv. vkt. akademiens handlingar, band 35. 



N:() 



outer side of the horn. It is less ansfnlar thtin the first, hut not so broadly ronnded 

 as the thii-d which befjins bas.dly on the median side. The thickness of this last is 

 4 mra. The dista.l part of the horn is quite smooth, proxiraally there can be seen irre- 

 uular transverse ridoes which are niost pronounced on the median side. 



The elements of the horny substance are, as can be plainly seen on a thin section, 

 longitudinall)' arransred. The core consists to a trreat extent of compact bony tissue. 

 It is espeeially strikinfj, when com]3ared with the condition fonnd in tlie gazelles (conf. 

 below), that the distal part of the oore of this Tragelaphns is almost compact for nearly 

 lialf its length the only exception being some few central canals for small bloodvessels 

 (conf. lig. ?), Pl. I). The proximal half of the core which is trihedral consists of a thick 

 outer compacta, biit the central parts are perforated by so many canals for bloodvessels, 

 rhat the}' nearly ha\e the appearance of a coarsely tubtdar spongiosa. In the base of 

 the core is foiiiid a small sinuous cavity (tig. 3) which, however, is less developed than, 

 for instance, that in Antiilorcas (conf. below) and does not stånd in connection with -mw 

 other sitius. The wall bordering this small sinus is thick, and espeeially on the posterior 

 side, compact. It is e\ident that horns of this structure are stronger than those of (V/y/ir?- 

 lophuK and may be advantageously used, not only agaiiist rivals of the same species, but 

 also against foes. Tlie ridges of the horny sheath are arranged in such a way that the 

 horns resend^le the T beams so greatlj' used in inechanical constructions. It is chiefly 

 the bases of the horns which are strengthened b)' this and liy the considerably increased 

 thickness of the proximal half of the whole organ, but the greatest resistance is just 

 ueeded at the tixed end of the lever \vhen the force is applied at the tip of the liorn. 

 But although the strength and the elasticity is increased by the .spinal ridges the horn)' 

 sheath is so thin that it needs a firm support from the core, and the structure of the 

 latter answers to this need as may be seen from the description above. Thanks to this 

 hrm support by the core the thin horny sheath does not ruri any risk of lieing corrngated, 

 and the greath' increased diameter of the basal part of the sheath adds to the power of 

 resistance in spite of the thin walls of the tube. The horns are probably used as spears, ' 

 hut when the sharp points have become iiiserted in the enerav the structure must be 

 firm enough to pre\eiit tiirsion and breakage aiid this is effected in such a manner as 

 lias been stated abo\e. — The spiral twisting of the horns during growth is produced 

 b)' strongev growth on tlie outer side especiallj' along the anterior and the latero-posterior 

 ridges. By this the horns become turned in opposite directions, the right horn being 

 twisted from left to right, the left one, on the contra ry, from right to left or, Avith other 

 words, the right horn foi-ms a left spiral and the left one a right spiral. 



It is easy to understa rid the reason why a horn becomes triangulär in section. A 

 ridge in the plane of attack is very useful in bracing the horn aiid adds to its jjower 

 ol resistance. Such a ridge may also originate as a result of meclianical irritation. If 

 two more similar ridges are developed in correspondence with the tirst one the horn 



*) That male antelopes of this genus sometimes wage earuest tights with each other is proved liy the 

 communication made by the experienced Eiiglish sportsman SELOUS (in Proc. Zool. Soc. 1881. p. 7ö4), who in- 

 forms US tliat hl' during his travels in South Africa, one iiioriiing found a iiiic ram of T. spel.ci lyiiig ilead 

 evidently killed in tigliting with a rival during the night. 



