514 



MESSRS. MIVART AND CLARKE ON THE SACRAL 



The 



Kg. 1. 



an osteological but not a nervous agreement with Man's second sacral vertebra. The 

 divergence consists in this, that whereas in Man the nerve issuing preaxially to every 

 sacral vertebra, except the last, goes entirely to the sacral plexus, Professor Gegenbaur 

 represents the nerve in Saurians which issues preaxiad of the second ilium-joining 

 vertebra as only contributing but a very small part of its fibres to that plexus 

 arrangement thus generally indicated by him is supported by descrip- 

 tions of the nervous conditions which he found to exist in a certain 

 number of different species. 



Professor Hoffman 1 has also given brief notices and rough diagrams 

 of the arrangement of the lumbar and sacral plexuses in a variety of 

 Batrachians and Reptiles. 



These two authors, however, do not agree in their account, nor 

 have we been fortunate enough to entirely agree with either of them ; 

 and, indeed, the discrepancies manifested by the species we have 

 examined have seemed to us somewhat noteworthy, and such as to 

 render it desirable that we should go somewhat further into detail as 

 to nerve-distribution than has been done in the memoirs referred to. 



Amongst the Lacertilia, Professor Gegenbaur has investigated the 

 composition of the lumbar and sacral plexuses in Chamceleo vulgaris, 

 Lacerta viriclis, Lacerta agilis, Uromastix spinipes, and Grammato- 

 phora barbata. Professor Hoffman has examined it in Chamceleo, 

 Monitor, Gecko, Lacerta viridis, Iguana tuberculata, Urothropus, and 

 JPolychrus marmoratus . We have made use of, for examination, Cha- 

 mceleo vulgaris, Monitor arenarius (two specimens), Lacerta viriclis, Teius teguexin, Iguana 

 tuberculata (two specimens), Agama colonorwm, and Grammatophora barbata. 



In our descriptions we shall make use of the following nomenclature: — The nerve 

 coming out in Lizards between the elongated transverse processes which abut against 

 the ilium we shall speak of as the intersacral nerve ; the nerve issuing out in front of 

 the more preaxial of these elongated transverse processes we shall call the first presacral 

 nerve ; the nerve still more preaxial we shall name the second presacral, and so on. 

 The nerve issuing out postaxial to the more postsacral of the two elongated transverse 

 processes we shall call the first postsacral nerve ; the nerve still more postaxial we shall 

 call the second postsacrcd, and so on. 



Nerves of Lizard (from 

 Gegenbaur). 



cr, crural ; is, ischi - 

 atic nerves ; other 

 letters and numbers 

 as in Plates. 





Nerves oe the Lumbar, Sacral, and Precaudal Region oe Lacertilia. 



Chamceleo vulgaris. (Plate LXVI. fig. 1.) 



According to Professor Gegenbaur 2 , the sciatic nerve in this animal appears to be 

 formed by three roots, one intersacral and two presacral, the first presacral being the 

 largest. The intersacral nerve gives off branches to the postsciatic nerves, while the second 

 presacral nerve bifurcates, giving one branch to join the third presacral, so forming the 

 crural nerve, which thus has but two roots. 



1 See ' Niederlandiscb.es Archiv fiir Zoologie,' Band iii. Heft 2, p. 143 (1876). 2 L. c. pp. 199, 200. 



