86 TIJE BONES. 



occipital tuberosity of which is very developed, the two angles in question are 

 nearly equal. In the Mule and Hinn//, the value of the angles is intermediate 

 between the Horse and Ass. In the Mule, the mean value has been 86 '12° for 

 the basilo-occipital angle, and 88° for the parieto-occipital angle. In the Hinny, 

 it was 87° for the first, and 81° for the second. 



E. Summit. — This results from the union of the four faces ; but, instead of 

 being acute, it is flattened from behind to before, curved from side to side, and 

 furnished with the incisor teeth.^ 



2. Conformation of the Cranium in Particular. 



Retzius was the first to start the idea of considering the cranium of Man 

 independently of the face. He distinguished the races of mankind as brachy- 

 mphalir (short-headed), and dolichocqihaUc (long-headed) — that is, crania long 

 from before to behind, and crania relatively short. Broca more recently compared 

 the transverse diameter of the cranium with the antero-posterior diameter taken 

 as a unit, and has expressed this relation in hundredths by the term cepludk 

 index. For some years, Sanson has endeavoured to introduce into the classifica- 

 tion of animals the calculations of Retzius and Broca. Taking the dimensions 

 of the cranium as a basis, he has divided Horses into two groups — the brachy- 

 cephalic and the dolichocephalic kinds. 



If the cerebral cranial cavity — the only important one for this purpose — be 

 enclosed in a parallelogram, two sides of which shall be at a tangent to the most 

 salient points of the parietal bones, and the other two pass in front of the 

 external auditory canals and across the supra-orbital foramina, the dimensions of 

 the base and height of this parallelogram, measured in a straight line, will 

 correspond to the longitudmal and transverse diameters of the cranium. In 

 proceeding thus, Sanson has found that in certain crania the transverse diameter 

 is greater than the longitudinal (brachy cephalic crania), while in certain others 

 the transverse is shorter than the longitudinal diameter {dolichocephalic crania).^ 



Toussaint took direct measurements of the interior of the cranium, and, no 

 matter what the breeds of horses were which he examined, he always observed 

 that the longitudinal diameter exceeded the transverse. We have made cranio- 

 metrical investigations on a number of Horses, and are able to confirm Toussaint's 

 statements. In eight skulls from different sources, the longitudinal diameter 

 varied between 113 and 133 millimetres, the transverse between 88 and 104 

 millimetres. Consequently, in none of these animals was the transverse diameter 

 equal to the longitudinal. In the number examined were the skulls of a Syrian 

 and an English stallion — types which Sanson would have selected as the most 

 brachycephalic ; the relations between the length and width were I'll for the 

 first, and 1'31 for the second. The average for the eight heads was r24. 



We are of opinion that there are no brachycephalic Horses, in the rigorous 

 sense of the word, such as Sanson admits ; so that, if it is attempted to establish 

 brachycephalic and dolichocephalic types, it will be necessary to previously fix 

 what shall be the limit between these two types, and this has not yet been done. 



The crania of Asses from the south of France are longer than that of the 



' For tlie regions of the head, see Lavocat's Nouvelle Osteologie rompar^e de la tete des 

 Animaux Domestiques. 



* Sanson, " Me'moire sur la Nouvelle determination d'un type specific de race Chevaline," 

 Journal de VAnaiomie et de la Physiologie, de Ch. Robin, 1867; also the later works of M. 

 Sanson. 



