128 ANTHROPOID APES. 



sacral form of the last lumbar vertebra, which stands 

 between the lumbar and sacral vertebrae, does not 

 indicate a gradual transition into a sacral vertebra, 

 but rather an arrest in its development.* 



When we examine a human sacrum we see that its 

 first vertebra, the twenty-fifth of the series, is formed 

 like the lumbar vertebrae in its upper part, setting 

 aside those portions of it which form part of the 

 lateral masses of the sacrum. These lateral masses, 

 which serve as a support to the ilia, owe most of 

 their substance to the first sacral vertebra. Thus, 

 since it has to support the whole weight of the pre- 

 sacral vertebrae, it is in fact a true vertebra fulcrdlis. 



Holl justly says that there are few instances in 

 which the human os sacrum consists of less than 

 five vertebrae, and in no case are there less than 

 four. In such a case the first sacral vertebra defines 

 the pre- and post-sacral segment of the vertebral 

 column. 



In anthropoids the lower segment of the lumbar 

 vertebral column is deeply sunk between the high, 

 wide, and flattened ilia, which converge closely 

 towards the vertebral column. In man these bones 

 are not so much higher than the base of the sacrum, 

 and their crests diverge more widely from the ver- 

 tebral column. In the large apes the lateral masses 

 of the sacrum are comparatively deeply set below 

 their anchylosis with the pelvic bones. In an aged 

 male gorilla, for instance, the transverse processes 

 of the two lower lumbar vertebrae often extend to the 



* Sitzungsherichte der Akademie der Wissenschaften zu Wien, 

 Ixxxv. fior. 1 : 1882. 



