KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 35. N:0 3. 25 



When this antelope iises its horns as vvea.pons, it evidentlv moves them in the sagittal 

 plane hooking from IjeloAv vipwards. The inechanical arrangenients are a.lso in accordance 

 Avith this. The greatest tension aflects the base of the horn, the fixed end of the lever. 

 This is also made very strong by arranging the resistant elements of the basal core in the 

 periphery of a wide tube. Both these basal tubes are also united on the median sido where- 

 by the hxation to the skull is made still firmer. The horn itself increases considerably 

 in thickness towards the base. In the a et of hooking the anterior side is pressed, the 

 posterior strained. A weaker portion of the horny shea,th corresponds, as may be seen 

 from the description above, to a thicker com])acta of the core, and at the same time the 

 trajectories are on that side of the bonv tissue more strongly and moro typically developed 

 in accordance with Culmann's law, that is, on the posterior side of the distal curve the 

 trajectories of stretching and on the anterior side of the proximal curve the trajectories 

 of pressure. But in such places in which the horny sheath is thick and firm enough to 

 endure the greatest tension alone, the trajectories are less typically developed and the 

 compacta weaker or missing. The elements of the spongious tissue are, however, in the 

 peripherical zone longitndiiially extended; thus to a certain degree substituting a com- 

 pact layer. The anterior side of the horny sheath is used to counteract the evil influence 

 of great pressure, corrugation. strengthened l)v means of the deAclopment of the transverse 

 ribs which are especially very strong in the distal curve. When the caama has (in the 

 act of hooking) lo\vered its head and with the sharp and elastic points transiixed some 

 object and then raises its hea-d, the distnl curve works like a hook. It ought tlierefore 

 to be strengthened, according to the mechanical ])rinciples, on the convex side in order 

 to obtain increased power of resistance. Such a thing has also taken place. This part 

 is, namely, strongly compressed from the sides, that is a »Verlängerung des Querschnittes» 

 in the plane of attack. The area of section is also ovate with the broad end on the inner 

 or concave side of the hook, A\-liieh thus becomes a cnrved T-l^eam. The, in this region, 

 very strongly developed transversaf ribs have also a strengthening effect. The trajectories 

 in this part of the core have already been spöken of. ^) Tlie middle-piece between tlie two 

 cnrves of the horn is, on the other hand, in the act of hooking influenced chiefly by a 

 force working in the same direction as its own axial extension. It is thus only subjected 

 to stretchino-, not to breakina' ijower. Tlie hornv sheath of this resion is then strong 

 enough to endure this strålning. The mechanical elements of the bony core are tlierefore 

 not especially arranged. This middle piece is also less thick than the adjoining as well 

 distal as proximal parts which prevents sliding. The proximal part of the horns must, 

 on the eontrary, htwe a considerablv [lower of resistance against a. lireaking foi-ce. It is 

 therefore, as has afrendy been stated, made Aery strong by the great Avidth of the horny 

 sheath and the firmness of the core in which the elements (if the spongiosa are ari-anged 

 according to CuLi\rANN's law. As the horns in their distal parts are somewhat bent out- 

 wards, a charge on the ti]) of the horn tends to eftect a breaking outwards and torsion. 

 To counteract this the l)asal parts of the hoiais are transversalh' thickened, so that the area 

 of section is lenghtened in the trontal (transversal) plane. lorsion and corrugation <if ihe 



') The straight tij) of tlio hook ciiii also bo regardod as a lever which tlioii imist be .sti-engtheiied especially 

 at its base, that is at the curve. In this case the same result is obtained. 



K. Sv. Vet. Akad. Handl. Baud 35. N:o 3. 4 



