44 THE STRUCTURE OF MAN 
From the above facts it is sufficiently evident that the 
vertebral column was ancestrally furnished with a far greater 
number of ribs than at present, and that the pleuro-peritoneal 
cavity or ccelom was once more capacious both at its cephalic 
and caudal ends. Even at the present time, as already shown, 
its modifications are not permanent. This is manifest, not only 
from the reappearance of (so-called “supernumerary ”) ribs, but 
also from the decidedly rudimentary character of the eleventh and 
twelfth ribs, which is rendered evident in several ways, more 
especially in connection with variation in their size. The twelfth 
rib, as might be expected, has a much wider range of variation 
(2 to 27 cm.) than the eleventh (15 to 28 cm.); neither pair of 
these reaches the sternum, and both show degeneration in their 
detailed relationship to the vertebral column. These ribs have 
no tubercle, and, consequently, no costo-transverse articulation ; 
and the articulation of the head (capitulum) of each of them is 
vertebral, instead of inter-vertebral, as in the case of those in 
front of them. Occasionally a tendency to similar conditions 
appears in the ninth and tenth pairs. Ontogeny shows that the 
reduction of the eleventh and twelfth ribs is comparatively 
recent, since the rudiment of the costo-transverse articulation 
(tubercle) of the eleventh rib is still developed in the embryo. 
Turning now to the ensiform (or xiphoid) process of the 
sternum, the variations in its shape, and more especially the 
presence of occasional median fissures or foramina in it, show that 
it arose from paired cartilages. It is, in fact, constricted off from 
the eighth, and possibly also from the ninth pair of ribs. The 
cartilages named, undoubtedly, at one time took part in the forma- 
tion of the “sternal bands” to be described later, and thus the 
number of ribs reaching the sternum may once have been greater 
as a strong process (Gegenbaur). These dower lateral spinous processes [anapophyses] 
which are found only in Hy/lobates, among Anthropoids, arising from the bases of 
the arches of the last two thoracic and sometimes from the first lumbar vertebre, 
according to Broca, occasionally occur in Negroes. It has been observed, further, 
that the spinous processes of the cervical vertebre, which are, as a rule, forked in 
Man, are simply pointed in the Hottentots ; and we here encounter a persistence of 
the original simple condition which is normal among Anthropoids (R. Blanchard). 
Finally, it should be mentioned, that the groove on the dorsal side of the arch 
of the human atlas for the reception of the vertebral artery is sometimes overarched 
with bone, and converted into a foramen, such as is always found in most Primates, 
Carnivora, and various other Mammals (Sappey). [And it is here worthy of remark 
that the costo-transverse foramen, and its homologue the vertebarterial canal, may 
in a similar way become completely surrounded by the transverse process 
(Hippopotamus, Man?). Cf. Jour. Anat. and Phys., vol. xxvii. p. 545. ] 
