THE CHIMPANZEES AND ORANGS. 105 



metapophysis (m); the rhomboidal form and downward inclination of the neural spine, 

 the base of which extends further down upon the lower zygapophysis (z') ; whereas this 

 process is more distinct and prominent, and has its articular surface more everted in 

 Man (fig. 5,;:). 



The contracted calibre of the neural canal in the lumbar vertebrae of the Gorilla, as 

 exemplified in fig. 4, is an interesting and important difference in its relation to the 

 minor development of the lower limbs in that great Anthropoid Ape. The superior 

 capacity of that canal in the corresponding Human vertebra (fig. 5) relates to the en- 

 largement of the myelonal centre of the supply of nervous influence to the characteris- 

 tically developed and modified lower limbs of Man, in relation to his privileged upright 

 posture. This difl^erence demands or occasions a greater length in the crura or bases 

 of the neural arch in the Human lumbar vertebrae. 



Thefirstlumbar vertebra of the Chimpanzee (PI. XXXV. fig 6)which, as in theGorilla, 

 answers to the second lumbar vertebra in the Orang and Man, differs from both in the 

 superior relative length and size of the neural spine (n s). The metapophyses (m) project 

 from the hinder and outer part of the upper zygapophyses, from which they are sepa- 

 rated by a narrow groove. There is a feeble rudiment of anapophysis from the lower 

 part of the long and depressed diapophysis (d). 



In the second lumbar vertebra the metapophyses still continue to be separated by a 

 groove from the anterior zygapophyses. The neural spine is more expanded at its 

 broad flattened termination. The centrum is somewhat augmented in size. 



In the third lumbar vertebra the diapophysis is shorter and thicker, and the anapo- 

 physial tubercle larger and more distinct at its lower part. There is a slight increase 

 in the size of the centrum. The neural canal, which, in the first lumbar vertebra, is 

 relatively narrower than in Man, becomes gradually more contracted as it approaches 

 the sacrum. 



The fourth lumbar, in the adult Chimpanzee examined by me, has had its diapophy- 

 sial elements modified for articulation with the iliac bones, and functionally forms the 

 beginning of the sacral series (Pi. XXXVI. fig. 3, I.) 



In proceeding with the examination of the vertebral column in the Ethiopian and 

 Australian varieties of the Human race, in reference to the present comparison, we see 

 that the lumbar vertebrae, five in number (Pi. XXXV. fig.2), are so arranged, when in their 

 easy and natural co-articulation, as to form a slight curve, with the convexity forwards ; 

 and owing to the less length of the bodies, these five vertebrae do not exceed by more 

 than half a vertebra the length of the four lumbar vertebrae in the Gorilla. Compared 

 with the dorsal vertebrae of the same Australian skeleton, the first lumbar vertebra 

 {ib. fig. 2, 1 ) has its centrum much increased in size, and the neural spine in extent. 

 The metapophysial tubercles (m) are also enlarged, but do not project so freely, by reason 

 of the extension of the articular surfaces of the upper zygapophyses upon the inner sides 

 of their base. The diapophyses are much increased in length. The anapophysial tuber- 



VOL. IV. PART IV. R 



