OP FISHES. 33 



BONES AND ARTICULATIONS. 



The skulls of fishes, more particularly the por- 

 tion including the brain, is the only compact part 

 of the skeleton. Bones without number seem to 

 penetrate the muscles, floating at one extremity 

 like the ribs of an umbrella. Next to the head, 

 the spine presents regularity and comparative so- 

 lidity. Joints, necessarily, are numerous, but dif- 

 fer essentially in structure from land anim.als. 



SKELETON OF AN OSSKUS FISH. 



Although serpents have spinal articulations, so 

 flexible that they can be tied into knots, without 

 injury to the spinal marrow, they do not possess 

 that freedom of motion which is so peculiar and 

 common to joints in the back-bone of fishes. 

 Each vertebra, entering into the composition of 

 the spine, instead of being locked into the next, 

 by hook-like processes of the bone, is excavated 

 at each end. Thus, when two are brought in 

 3 



