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, 2). 
The contracted calibre of the neural canal in the lumbar vertebre 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 difference demands or occasions a greater length in the crura or bases 
of the neural arch in the Human lumbar vertebre. 
The first lumbar vertebra of the Chimpanzee (P]. XX XV. fig. 6) which, as in the Gorilla, 
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 (ns). ‘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 (Pl. XXXVI. fig. 3, /.) 
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 vertebre, five in number (Pl. 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 Jength of the bodies, these five vertebrae do not exceed by more 
than half a vertebra the length of the four lumbar vertebra in the Gorilla. Compared 
with the dorsal vertebree 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 
