450 PITHECANTHROPUS ERECTUS. 



Disregarding this, some believe that the skull may have belonged to 

 a true ape. If we should imagine the' skull of Hylubates agilis to have 

 somewhat more than doubled its mass, we should have a skull of a 

 similar great ape. But if in actual fact a Hylobates had reached such 

 a size, it is quite certain that his cranial capacity would not have in- 

 creased in the same degree, for we continually find in the most diverse 

 families that large animals have relatively smaller brains than smaller 

 allied species. For example, the dwarf antelope (JS r anotragus pyg- 

 ma'us) has in proportion to its bodily weight more than four times as 

 much brain as the Beisa antelope. 1 The smaller lower apes very much 

 surpass in this respect the large anthropoid apes, and the gibbons 

 possess, in proportion to their bodily weight, at least twice as much 

 brain as the great anthropoids. 2 



Such an imaginary gigantic Hylobates would be about as tall as a 

 man and about as heavy as the great anthropoids. Its cranial capacity 

 would therefore not exceed some 500 c. cm. But this is only a little 

 more than that of Pithecanthropus. A true ape with a capacity of 900 

 c. cm., must, on the contrary, be a giant besides which the largest 

 gorillas would be dwarfs. Even if the bodily size increased only in 



cavity of the skullcap so that I could compare the dimensions of the cranial cavi- 

 ties, two other methods were also used by me, as follows : 



A. (1) The external volume of a skullcap above a plane passed symmetrically 

 through the glabella and the external occipital protuberance was determined. 

 (2) Its surface was found by weighing a tin-foil covering that had been spread over 

 it. (3) Its internal capacity was approximately determined by deducting from the 

 value found under (1) the product of the surface found under (2) with the medium 

 thickness of the skull plus the volume of the frontal sinuses. From the result thus 

 obtained (540 c. cm.) the capacity of the entire Pithecanthropus skull was estab- 

 lished by (4) comparing with it skulls of Hylobates of as similar build as possible, 

 whose skullcap capacity and total cranial capacity has been determined by direct 

 measurement. 



B. After the siliceous matter had been for the most part removed from the skullcap, 

 this was also directly measured by rilling it up to the above-mentioned plane with 

 mustard seed and adding to this volume the estimated volume of the siliceous mat- 

 ter yet remaining. I found that the above-mentioned portion of the cavity of the 

 skullcap measured about 550 c. cm. The cast of the cavity of the Neanderthal skull 

 taken to the same plane measures 750 c. cm. 



It is well known that Huxley estimated the entire capacity of the Neanderthal 

 skull at 1,236 c. cm. The ratio of the capacity of the skullcap to that of the entire 

 skull is, therefore, 3:5. In a skull of the Hylobates agilis, which, though only half 

 the size, strikingly resembles that of Pithecanthropus, I find the same ratio. 



According to all these methods, the total cranial capacity of the Pithecanthropus 

 skull is found to be 900 c. cm., or somewhat more. The difference between this and 

 my earlier estimates (compare also the Verhandl. der Berliner Gesellschaft fiir 

 Anthropologic, 1895, p. 728) depends upon this, that in the first I did not allow suffi- 

 ciently for the thickness of the skull (it is about 6 mm.), and secondly I could not 

 directly compare the cavity of the skullcap. 



1 Accordiug to Max Weber, Waarnemingen over het hersengewicht van zoogdier- 

 nen. Bijdragen tot de Dierkunde, Amsterdam, 1888, p. 14. 



-Compare the statements of Owen, Comparative Anatomy, Vol. Ill, p. 143, and 

 M. Weber, Zool. Ergebnisseeiner Reise iuNiederlandisch Ost-Indien, pp. 99, 100. 



