MYOLOGY OF EEPTILES. 231 



There are small modifications of the muscles of the long anterior 

 outstretched ribs of the Coljra, fig. 46, jil, which sustain the 

 peculiar folds of integument forming the conspicuous ' hood ' of 

 that poisonous snake. These ribs are protracted or raised by the 

 Icvatores breviores, and by two sets of pretrahentcs, one passing- 

 over two ribs to the third behind, Ihe others passing over one 

 rib to the second, and by the intercostales externi. The muscles 

 passing from the hood-ribs to the skin come off" about fijur lines 

 I'rom the head by a short tendon, the fleshy band extending 

 Ijctween one and two inches, outward and backward to its inser- 

 tion into the skin. 



The muscular system of the trunk reaches, in Reptiles, its 

 maximum in Serpents ; it is reduced to a minimum in Tortoises : 

 yet, where it has to act on the only moveable part of the verte- 

 Ijral column of these slow and heavy house-l)earers, it is specially 

 and in some parts largely dcA'cloped. 



Homology can seldom be determined or discerned, save in a 

 general way, in the fleshy parts of Clwlonia ; as, e. g., that the 

 muscles upon or about the triuik-vcrtebraj answer to those so situ- 

 ated in lower or higher Vertebrates ; and that the primitive seg- 

 mental character of such muscles is still indicated by distinct and 

 successive attachments to a consecutive series of bony segments, as 

 is shown, e. g., in fig. 148, 37, 39, fig. 149, 27. AVhere a more 

 special determination has been attem])tcd it has usually rested on 

 a similarity of attachment of one end of a muscle, with acknowledged 

 discrepancy at the other end; as when Cuvier' compares 27, fig. 

 148, to the sacrolumhalis and hmgissirnus dorsi ; and when Bojanus^ 

 gives the latter name to the portions of myocommas at the opposite 

 side of the back-bone, fig. 148, or calls the muscle, fig. 152, 9i, 

 which arises from the pubis, the iliacus internum. It will be 

 understood, therefore, that in applying to the muscles of the Box- 

 tortoise {Emys Eiiropa'a), the names assigned to thcni by the 

 author of the exemplary and beautifid monograph' from which 

 the illustrations, figs. 148 — 159, have been copied, they are to be 

 taken more or less in an ai'bitrary sense, and that the characters 

 of the muscles mainly exemplify the greater degree in which the 

 adaptive jirinciple prevails over the archetypal one in the soft than 

 in the hai'd parts of the frame. 



On the dorsal aspect of the vertebra; of the back, the muscular 

 system is restricted to the ' xpmalls dorsi,' fig. 148, 39 ; it rises 

 from the neural and beginning of the costal plates, neural arch 



' XIII. i. p. 292. ^ xxxviii. '■' lb. 



