26 LECTUEE II. 



living men. Thus while vou Baer, for instance, with many 

 otherSj measures the diameter of the skull from the lowest 

 point of the forehead, the so-called glabella, to the most pro- 

 jecting point of the occiput, Welcker takes the frontal emi- 

 nences, which are situated higher up and cannot be exactly 

 determined either in the living or the dead skull, as his start- 

 ing-points, so that both these measurements are liable to 

 great objections, both on the score of usefulness and accuracy; 

 this much, moreover, is certain, that, even if they could be 

 accurately determined, they are not comparable with each 

 other. 



There is another circumstance, as von Baer justly observes, 

 which, must be attended to in cranial measurements, namely, 

 the unequal thickness of the skull in various parts, so that in 

 order to obtain an approximative idea of the internal capacity of 

 the cranium, we must select the points where the bone is thin- 

 nest, and avoid the prominences, which are especially Hable to 

 be modified by the action of the attached muscles. 



On each side of the human skull there is a curved line, the 

 so-called temporal ridge, which marks the limits of the tem- 

 poral muscle. The more this muscle — the chief masticating 

 muscle — is developed, the higher up is the line, and the broader 

 the space between the zygomatic arch and the cranium. The 

 development of this muscle is sometimes so great that in many 

 animals its fibres have no room for attachment to the side of 

 the skull, and a crest is formed on the vertex to serve for at- 

 tachment. The development of the temporal ridge and the 

 breadth of the zygomatic arch are, therefore, in direct propor- 

 tion, both depending on the development of the temporal 

 muscle. Now, it is this muscle which especially efiects the 

 perpendicular action of the jaw ; whilst the lateral motions of 

 the jaws, for the grinding of the food, are efiected by other 

 muscles. The latter are greatly developed in vegetable feeders, 

 such as ruminants, whose lower jaw acts like a millstone. The 

 perpendicular motion especially obtains in carnivora. We thus 

 necessarily arrive at the resiilt, that nations living chiefly on 

 animal food exhibit more developed temporal ridges and broader 

 curved zygomatic arches than vegetable feeders j the latter pos- 



