FRAGILITY OF THE TAIL IN LIZARDS 113 



tebrae are left intact, or may be so left, and there 

 is seen a number of fibrous septa running from the 

 vertebral processes to the integument, thus dividing 

 the tail into compartments into which the muscles are 

 fitted, and out of which the thin tapering ends readily 

 escape when the fracture occurs. The diagram on 

 the opposite page shows the arrangement of these 

 septa. 



These septa are not continuous longitudinally, but 

 each is inserted into the integument of its own 

 segment, opposite the end of the scales of that 

 segment, so that here the fracture takes place. Here 

 again, as in the slow-worm, the proximal end of the 

 fragment of tail shows the eight muscles protruding, 

 while the distal end shows the intervertebral articu- 

 lation surface intact, the fracture having occurred 

 behueen two vertehrce, not across one. On illustration 

 facing page 108 these two ends are seen photographed 

 from the fresh dissection. Both these fractures show 

 the articulating surfaces of the vertebrae intact. In a 

 word, there is no fracture of the caudal vertebrae in 

 these cases, but a simple disarticulation or dislocation. 



It was thus concluded that fracture of the tail in 

 the green lizard, as in the slow-worm, depends mainly 

 upon the pecuhar arrangement of muscles and integu- 

 ment ; that this fracture takes place or may do at 

 definite intervals corresponding to the end of every 

 second caudal scale ; and that this position as regards 



the caudal vertebrae was at an intervertebral articula- 

 8 



