126 
ORIGINAL ARTICLES. 
so that it is doubly united with the body.” The propriety, how¬ 
ever, of considering the head and neck of a rib as a process is highly 
questionable. Professor Huxley, # from whom I have quoted this 
translation of a passage in Bathke’s Entwiclc. der Natter , has been led 
by observations on the embryo Mouse to the precisely opposite con¬ 
clusion, that the mammalian ribs are not primarily connected with 
the transverse processes, but are primarily contiguous with the 
centra of the vertebrae. The opinion at which I have myself arrived 
is quite in accordance with Prof. Huxley’s observations, yet differs 
from both his conclusion and Rathke’s. 
I maintain that the costo-vertebral and costo-transverse articu¬ 
lations are mere subdivisions of an articulation which in certain 
cases is found single. I am convinced, from observation of young 
human and other skeletons, and, indeed, from Prof. Huxley’s wood- 
cuts of vertebrae of the embryo Mouse, that the early connexion of 
the rib to the vertebra includes both the articulation of the head and 
of the tubercle, that the transverse process is developed from the 
part of the vertebra already in contact with the rib, and that the neck 
of the rib is formed pari passu with the transverse process. 
This view is very well illustrated in the back part of the thorax 
of the Horse. In the articulation of the last rib of the Horse there is 
manifestly an anterior inferior portion, corresponding to the articu¬ 
lations of heads of ribs further forward, and a posterior superior por¬ 
tion distinctly costo-transverse in nature. Perhaps we shall also 
be justified in considering, in the case of Serpents in which the 
vertebra presents for articulation with the rib a concavo-convex 
surface, that the anterior inferior concave part articulates with the 
round head of the rib, and that the remainder of the joint corresponds 
to the costo-transverse articulation, in which, according to the general 
rule, the convexity is on the vertebra. 
Peturning now to the question, whether the transverse process or 
the articular surface for the head of the rib in the mammal corre¬ 
sponds to the ordinary transverse process in the fish: it is important 
to notice that the correspondence of structures is a thing of degree; 
that the transverse process of the mammal corresponds to that in the 
fish, in respect that it is an element of the primary circle or costal 
arch; and that the articular facet for the head of the rib, especially 
if elevated on a process, has also that amount of correspondence to 
the fish’s transverse process, with the additional less important resem¬ 
blance of arising sometimes from the centrum; while both processes 
together, the mammalian ‘ diapophysis’ and ‘parapophysis,’ correspond 
to the ordinary transverse process or ‘ parapophysis ’ in the fish, in 
respect that they together form the base from which the rib starts 
outwards on its course round the visceral cavity. Only in this 
manner can all the facts be reconciled. 
* Loc. cit. pp. 69 to 74. 
