74 THE STRUCTURE OF MAN 
shoulder girdle is loosely attached to its ribs by muscles, the 
pelvic by firm ligaments and a definite articulation.’ 
In the human embryo, as in all living Reptiles, Birds, and 
Mammals, the embryonic pelvis is triradiate, its cellular blastema 
at first forming one mass with that of the developing femur: this 
condition I have traced through the whole series of Vertebrates.? 
After the pelvic blastema has, at a later stage, become differ- 
entiated from that of the femur, which is the first to become 
cartilaginous, the ilium, ischium, and pubis are laid down as 
distinct chondrifications. The fusion of the acetabular portion 
of these three pelvic cartilages takes place in the following 
order: first, the ischium alone unites with the ilium, and later, 
the ilium with the pubis. The ischium and the pubis do not 
send out acetabular processes towards one another, and for this 
reason a space is left at their point of apposition. 
[The bone to which in the adult human subject the term 
pubis was first apphed, is formed by the union of two distinct ele- 
ments——-a main one arising 7 utero, and a lesser, arising during 
the thirteenth year * within the acetabular region, and completely 
excluding its neighbour from that cavity. The latter element 
is of regular occurrence among the lower Mammalia, and being 
in them of considerable proportions has received the name 
“cotyloid bone” or “os acetabuli.” In accordance, however, with 
its ultimate fate, it may be more appropriately termed the 
dorso-pubic element, and its neighbour the ventro-pubic.* Thus 
considered, comparison of the pubis with the coracoid (ante, 
p. 72) shows that in Mammals, and in them alone among living 
Vertebrates, each consists of two elements, of which one 
(epicoracoid and pre-pubic element) is excluded from the 
articular facet (glenoid cavity and acetabulum). | 
In no other Mammals do the iliac bones diverge so greatly 
1 This difference appears less marked, and may altogether vanish, when we 
compare the [lower vertebrata. Among Chelonians the shoulder girdle very generally 
articulates upon the anterior thoracic vertebre ; and in] Fishes a firm connection 
is established between the shoulder girdle and the skull (Osteichthyes), or even 
between the former and the vertebral column (Rays), [such as is seen also in many 
Frogs and Toads, and may, under rare conditions, occur in Man himself.] In 
certain Salamanders we find, on the rib approximate to the inner border of the 
suprascapular, a plate-like cartilaginous expansion, which is fastened to the shoulder 
girdle by means of ligaments ; [this, however, has probably to do with protection of 
an adjacent pulsatile ‘‘lymph-heart.’’] 
2 The author here refers in the original German to his ‘‘ Gliedmassen Skelet der 
Wirbelthiere,” Jena, 1892. 
3 (Cf. Krause, Month. Internat. Jour. Anat. and Hist., vol. ii. p. 150.] 
4 (Cf. Howes, Jour. Anat. and Phys., vol. xxvii. p. 550.] 
