KONGL. SV. VET. AKADEMIENS HANDLINGAK. BAND 35. N:0 3. 5 



side of the beaiii at ;ni aiigle of [Hf. The tvajeetories of pressui/e origiiiate at tlie lower 

 compressed surface and beino" at lii'st [jarallel to the same tlicy make a similar curvc 

 in a direetion opposite to that of tlie trajectories of stretchiny. Both .systems of eur\es 

 eonsequently cross eaeli other at an angle of 90° in the neutral axis. In order to make 

 a beam, or similar body or eonstruetion, capable of retaining its shajje and resistant 

 against breakage wlien charged in such a way as described above, the material A\'hich can 

 endiire and resist stretching and pressure ought to be arranged along these trajectories 

 for the ]iurpose of (jbtaining the greatest efticieney. This rule is ai)plied by natui'e in 

 the spongious tissue of luany skeletal bones as has been proved by the authors (pioted, 

 and by others. In the following it will be shown that the same arrangement takes ])lace 

 in the substantia spongiosa of the horn-cores, too, Avhen it is ueeded. x\lthough the 

 function of the horn eores is different to that of the skeletal l^ones, as has been alluded 

 to above, they might suitably Ije likened to le\'ers fixed at one end and when used a 

 eci'tain force is applied to the free end. Culmann's laM' may aceordinglv find an 

 applieation also in this case. 



It might be assumed as axiomatie that from tlie beginning the primitive horns of 

 the Cavlrornia originated as exostoses on the frontal bones witli a härd dermal eovering. 

 These exostoses were naturally solid so that they could resist \iolent force. By and by 

 ihe liorny sheath beeanie more and more developed, bnt it was from tlie bisginning only 

 a thin eovering and the strength of the horn lay entirely in the eore. The horny sub- 

 stance becanie, hovvever, usefnl for d(juble purposes. Firstl)-, it gave ])roteetion to tlie 

 underlying tissue, the superlieial nourishing bloodvessels, the nerves etc., thus lessening 

 the general susce])tibility and sensibility of the organs. Secondly, the hornv substance 

 furnished \\ith sharp and more elastic points so that the organs became more effective 

 weapons at the same timc as the tips ran less risk of being Ijroken. 



Horns re])resenting such a rather primitive stage are still found in several ante- 

 lopes. As an example of this Ceji/ialop/uis inav be chosen. I have made seetions through 

 the horns of C. syloicidtor (Afzelius) ? and (•'. (Jnrsidi.s O. Thomas ef of this genus. Both 



f theni sho-\ved similar conditions. The short spikelike horns are solid without trace of 

 any sinus in the core. The bony tissue is very dense and can be said to consist only 

 of substantia compacta. But the core is of course traversed by longitudinal canals and 

 pores for the bloodvessels (conf. tig. I, Pl. 1). In the centre of the core these are largest 

 and inost numerous. In the centre of the basal portion the canals are partly confluent 

 and partly only separated by thin lamellaB of bone (C sjjlclcultor). This region gets 

 therefore a somewhat porous aspect. There is however no substantia spongiosa or tyiiical 

 spongious bony tissue to be seen an)'\vhere. Compared Avith the size of the core the 

 structure is eonsequently very finn. The horncores are in Cephalop/ius quite conical in 

 sliape. In a specimen of C. dorsidis the h^ngth of the core ineasures 40 mm. and the 

 basal diameter of the same is 12 mm. It is thus comparatively stoutJ) The horns of 



"'.iiii---'! ,., •,,• ,1 i .-- iii:-I-iiil I ni .,iu<i '^ 



') In soine otber species as for instance Cephalojiliu.'< ogilbyi the horns are still thicker. In a specimen 

 of this kind the greatest transvcrse diameter of the horn (with the sheath) is 37 "» of its leugth. Accordiiig 

 to SCLATER and Thojias the greatest basal diuraeter goes 2' 2 or 3 times in tlieir length. (Uook of the aiite- 

 lopus p. 1(J2). ... 



O 



