3 io THE POPULAR SCIENCE MONTHLY. 



while I set out a few details to show the several factors whose 

 influence should be numerically indicated by such a mode of 

 measurement. 



The parts composing the skull may be resolved into four sets : 

 there is, first, the brain-case ; secondly, the parts which subserve 

 mastication and the preparation of the food for digestion ; thirdly, 

 the cavities containing the organs of the senses of hearing, sight, 

 and smell ; and, fourthly, those connected with the production of 

 articulate speech. If our measurements are to mean anything, 

 they should give us a series of definite numbers indicating the 

 forms, modifications, and relative size of these parts, and their 

 settings with regard to each other and to the rest of the body. 



To take the last point first, it needs but a small consideration 

 to show that the parts of the skull are arranged above and below 

 a certain horizontal plane, which is definite (although not easily 

 ascertained) in every skull, human or animal. This is the plane 

 of vision. The familiar lines of Ovid — 



"Pronaque cum spectent animalia cetera terrain, 

 Os hornini sublime dedit; coelumque tueri 

 Jussit, et erectos ad sidera tollere vultus " * — 



are anatomically untrue, for the normal quadruped and man alike, 

 in their most natural position, have their axis of vision directed 

 to the horizon. Systems of measurement based upon any plane 

 other than this are essentially artificial. There are at the outset 

 difficulties in marking the plane accurately on the skull, and it is 

 to be deplored that the anthropologists of different nations should 

 have allowed themselves to be affected by extraneous influences, 

 which have hindered their unanimous agreement upon some one 

 definite horizontal plane in craniometry. 



The Frankfort plane, drawn through the upper margins of the 

 auditory foramina and the lowest points of the orbital^borders, 

 has the advantage of being easily traced, and differs so little 

 from the plane of vision that we may without substantial error 

 adopt it. 



The largest part of the skull is that which is at once the re- 

 ceptacle and the protector of the brain, a part which, when unmodi- 

 fied by external pressure, premature synostosis, or other adventi- 

 tious conditions, owes its form to that of the cerebral hemispheres 

 which it contains. Speaking in this city of George and Andrew 

 Combe, I need not do more than indicate in this matter that 

 observation and experiment have established on a firm basis cer- 

 tain fundamental points regarding the growth of the brain. The 



* While other animals look down upon the earth, he has given an upward face to man ; 

 and has ordered him to look at the sky and to raise his eyes to the stars. 



