SKELETON. 



observed to occupy the interval between (e, d) two clavicles are required to be metamor- 



the ischiadic and pubic bones, and (3, 4, 5) phosecl from ribs, they illustrate still further 



t he sacral vertebras. The junction between 



the ilium and the sacral vertebras is called 



sacro-iliac, whereas by the union of the ilium 



(//, //) with the pubic and ischiadic bones (d,e), same character that the clavicles manifest in 



the articular cup called acetabulum (g) is relation to the scapula. 



formed. While the ilium becomes thus inter- 



the structural analogy which exists between 

 them and the ischiadic and pubic bones, which 

 latter exhibit, in relation to the ilium, the 



becomes thus inter 

 calated between the pubic and ischiadic bones 

 on the one hand, and the vertebrae on the 

 other, it severs the former from connection 



In Jig- A. the os penis (/*) will be seen to 

 fall behind the symphisis pubis, while mjjg. B. 

 the episternal ossicles (/*) will be noticed as 

 producing the sternal median line forwards 



but in the comparative abstract animal, these 

 points may be regarded as unfinished. 



PROP. XL IV. The crania-facial apparatus 



with those vertebrae to which, as costas, they into the neck. At the subpubic region, where 



properly belong; and it obliterates that costal /* occurs, and at the episternal region, where 



quantity indicated in dotted outline at 3, 4, 5, the episternal ossicles occasionally appear, the 



which quantity, if it still persisted, would sternal median line is bounded in' the animal 

 unite the pubis and ischium to their proper 

 vertebrae. In fig. 491. I have represented in 



A some of those lineae transverse (a. b, c), __ . . _ ., ..,.,_.,, 



winch sketch out the form of the original of segments are proportionals of the dorso-ventral 



ventral ribs proper to the lumbar vertebras ; archetypes. If it be true that the vertebral 



and it will be seen that a, 6, c hold series quantity is a proportional of the sterno-costo- 



with (f/)the pubic bone, and (e) the ischiadic vertebral quantity, and this latter a propor- 



bone. Between a, b, c, as the ventral ribs, tional of the dorso-ventral archetype, then it 



occur the intercostal spaces (//), and be- must follow that the cranio-facial apparatus, 



tween the pubic and ischiadic bones (d, e) which appears to bear a structural homology 



occurs that space (/) which, in human ana- with the sterno-costo-vertebral quantities, is 



tomy, is named " thyroid foramen." Is not also constituted of segments which, like these 



this thyroid foramen an intercostal space, if latter, are proportionals of the archetypal 



d and c be costas proper to the sacral vertebras? quantities. Even though the whole animal 



And do not the pubic and ischiadic sym- kingdom did not present us with a skeletal 



phises at the point /. correspond to the linea form, upon whose cranium the dorsal rays 



alba (/, /), which stretches between the pubis persisted complete, still the above-mentioned 



and sternum. inference may be legitimately drawn; but 



when, amongst the class of osseous fishes, we 

 fiudfig. 492., upon whose cranium the dor- 

 sal rays actually persist, then the d priori and 

 the d posteriori trains of reasoning meet and 



B. we find the scapula (k, k, h, f) oc- 

 cupying, at this region of series, a position 

 similar to that which the iliac bone holds 

 elsewhere. But beneath the scapula the ribs 



(-> 3, 4), for obvious purposes, persist ; while answer to each other, while standing in pre- 

 beneath the iliac bone they are wanting. This sence of the fact itself, as nature produces it. 

 want of the ribs beneath the iliac bone, and In fig. 492. we see that the archetypal 

 this presence of the ribs beneath the scapula, dorso-ventral quantities (a,b,c,d) are conti- 

 constitute the difference. nued into the head, not only by their centra, 



^ If those portions of the ribs (b and c of their costal inferior arches, arid their dorsal 

 fig. B.) which lie beneath the scapula suffered 

 metamorphosis, then b and c would abut upon 

 the glenoid cavity h, and would be to the 

 scapula what the pubic and ischiadic costiform 

 bones are to the ilium ; and then we should 

 have, between b and c of fig. B., the inter- 

 costal space/ as corresponding to the thyroid 

 aperture. It is the costiform clavicle (a of B) 



laminae, which form the neural arches from 17 

 to 1, but also by their dorsal interspinous os- 

 sicles from in to n, and by their dorsal palms 

 from o to p. 



The head of the osseous fish (fig. 492.) of 

 the class Pleuronectidse may be accounted, 

 therefore, as constituted of a series of the 

 dorso-ventral archetypes specially modified. 



is continued the line of spinal centra ; and 

 from these, as from the centra elsewhere 

 throughout spinal series, the dorsal and the 



mi r~ . _- i 



which becomes severed by the scapula from Between the cranial and the facial structures 

 its vertebra behind, just as the costiform os 

 pubis is severed by the iliac bone from its ver- 

 tebral quantity. 



The cotyloid cavity (g of A) is formed by ventral rays' project. The inferior cranial 

 the junction of three bones, viz. the ilium rays are the jaw-bones (c f. h h) and hyoid 

 (h h), the os pubis (d), and the ischium (e) ; arches (g, g) ; the superior cranial ra\s are 

 but it is the iliac facet of the cotyloid cavity the forms o p, m n. 



which alone corresponds to the glenoid cavity PROP. XLV. The rranio-farial apparatus is 

 of the scapula. If the ribs (6 or c of fig. B.) the origin of the dorso-ventral archetypal series, 

 happened to be dissevered from their vertebras 

 behind by an interval equal to the size of the 

 scapula (k, k, //), and if these sternal ends of 

 the ribs (b, e) then joined themselves to the 

 glenoid articular surface (h) of the scapula, 



and the caudal apparatus is its termination. 

 In the same animal, whose cranial structures 

 are still crested by the dorsal rays complete, 

 we find the opposite caudal extreme (fig. 493.) 

 also crested by similar rays, dorsad as well as 



the three bones (ti, b, and c) would also form ventrad. The spinal centra (n, m, I a) still 

 a cotyloid cavity for the head of the humerus. produce the entire rays (o, (j) above and be- 

 In those animals (birds, reptiles, &c.), where low, while the terminal centrum () stands as 



VOL. IV. 



X X 



