VOL. XX.] PHILOSOPHICAL TRANSACTIONS. 203 



inch long. The 6 following vertebrse of the thorax have short, thick, and 

 flat spines: the obliqne processes being continued on each side of the spine, 

 make as it were a gutter ; and the transverse processes here are somewhat 

 different from the former. The spines of the vertebras of the back, or loins, 

 as they approach the os sacrum, lessen gradually in their thickness on the edge : 

 but here were double oblique processes, viz. four at each end of the vertebra, and 

 the undermost spreading themselves out in breadth. The three vertebrae of the 

 OS sacrum are firmly fastened to the os ilium ; but the last not so entirely as 

 the two former, which at each side had a broad transverse process, and the 

 spines of these were thin. The first two vertebrae of the tail had only one 

 small acute spine ; but in all the other vertebrae of the tail, both at the head 

 and tail of each vertebra, there were two spines ; but those at the head of the 

 joint, the larger. In the first 6 vertebrae of the tail, there was on each side a 

 broad transverse process, the length of the joint : in the other vertebrae only 

 at the head and tail a jetting out at the sides. The vertebrte about the middle 

 of the tail, were the longest ; being there about an inch long; nearer the root 

 of the tail, and at the end not so long. 



But there is a wonderful piece of nature's mechanism, in those spines or 

 hooks, placed in a line in the middle of the under side of the vertebrae of the 

 tail. It is true the first three vertebrae had none of these spines, nor were they 

 necessary here, since they lay within the compass of the ossa coxendicis ; but 

 in all the other vertebrse, to the end of the tail, they were to be observed ; and 

 as they approached the extremity of the tail, they grew less and shorter. 

 These spines, where longest, were about 4- of an inch, or somewhat more : 

 they were placed just at the articulation of each joint, and in the middle from 

 the sides, and seemed to be articulated, both to the preceding and following 

 vertebra ; not being an entire solid bone, but rising from the vertebrae with the 

 crura or legs, become afterwards perfectly united at the ends. By this means, 

 these bones are rendered more firm and strong, and this hollow serves for 

 transmitting the blood-vessels through them ; and one may here observe a stria, 

 or furrow, all the length of the vertebrae, for receiving them ; by which they 

 are the better secured from compression, when the animal hangs by its tail : 

 arid for performing this office, nothing could be more advantageously con- 

 trived : for when the tail is twisted or wound about a stick, this hook of the 

 spine easily sustains the weight, and there is but little labour of the muscles 

 required, only sufficient for bending the tail ; for then, as by a hook, the 

 weight ot the whole body is here suspended. And for performing this, it was 

 observed, that in each precedmg vertebra, there arose a muscle, which was 

 inserted on each side of the succeeding vertebra ; which acting or contracting. 



