448 



ends, the process commencing very soon after the ossification of the 

 centra ; but after ossification has begun in them, these originally filiform 

 parts widen into broad oblong plates, which, in the greater part of the 

 body, come into contact only towards the end of the period, and in the 

 tail and hindermost part of the body, only in the following period. 



" The ribs ossify far later, and also from the middle towards the end. 

 Before, however, an ossific centre is developed in them, the cartilage, of 

 which the rib now for the most part consists, becomes articulated with 

 the rest of the vertebra. The plate, lastly*, which forms the union 

 between a rib, a vertebral arch and a* vertebral body, and subsequently 

 forms a part of the body of the vertebra, ossifies only in the following 

 period. 



" The relation of the ribs to the bodies of the vertebrae, therefore, is 

 originally just the same as that of the crura of the vertebral arches to 

 them : just as one of these crura, does each rib arise as an outward growth 

 of that vertebral body which is the first formed of all these parts ; whilst, 

 however, the crura of the vertebral arches are directed upwards in order 

 to enclose the spinal cord, the ribs grow downwards to enclose the viscera 

 of organic life, and in this way their greater length in the snake, and a 

 multitude of other Vertebrata, is explicable. 



" The transverse processes of the caudal vertebrae exhibit the same rela- 

 tions to the bodies of the vertebrae, as the ribs in the dorsal region. They 

 arise in the same places as these; become, in like manner, removed, together 

 with the crura of the arches, by lateral outgrowths of the body from its 

 axis j and, before the ribs are articulated, they pass quite imperceptibly into 

 the processes in question. The transition is the more remarkable, as in the 

 snake the hindermost rib is split, in just the same manner as the transverse 

 processes of the three or four succeeding caudal vertebrae. 



" If we consider, in the first place, the relation of the parts in the adult 

 snake, we find that the penultimate rib, near its upper or inner end, 

 gives off from its upper side, a small process directed upwards and out- 

 wards ; however, in the last rib this process is about a quarter as long as 

 the remaining part of the rib, which lies external to and below it, so that 

 the whole bone has the form of a two-pronged hay-fork, not yet fastened 

 to a handle, and one of whose prongs is for the most part broken off. The 

 same fundamental form is possessed by the transverse process of the first 

 caudal vertebra ; and the difference between it, and the rib which lies 

 immediately before it, lies principally in this, that it is not, like the rib, 

 articulated with its vertebra, that its upper half or prong is almost equal 

 in length to the lower, and that, regarded as a whole, it is not half so long 

 as the hindermost rib. The transverse processes of the succeeding caudal 

 vertebrae have quite the same form as their predecessors, but gradually 

 diminish in length backwards. As to the development of the ribs and 

 transverse processes in question, they, like almost all the other ribs, are 

 originally sent out as quite simple rays from the bodies of their vertebrae ; 

 very soon, however, there arises on the upper side and neck of the ray 

 where it passes out from the vertebral body, an outgrowth which elongates 



* Paraphysial cartilage. 



