524 



MESSRS. MIVART AND CLARKE ON THE SACRAL 



Kg. 5. 



ilium ( 

 d' 



Nerves of Cryptobranchus (from 

 Humphry). 



Fig. 6. 



enlarged transverse process, while the third is postaxial to it, the ohturator and crural 

 nerves being formed by two roots, one preaxiad to, the other 

 coincident with, the most preaxial root of the sacral plexus. 

 The third spinal nerve, preaxial to the ilium (fig. 5, a), bifur- 

 cates, one branch forming the obturator nerve (fig. 5, ob), the 

 other contributing to form the crural (a.cr). The second spinal 

 nerve, preaxial to the ilium (b), also bifurcates, one branch 

 joining the postaxial bifurcation of the preceding nerve to form 

 the crural, the other joining the spinal nerves, pre- and post- 

 axial to the ilium (c & d), to form the sciatic (sc). Hoffman merely cites 1 Professor 

 Humphry, and he gives a wrong reference. 



In Salamandra maculosa and Triton cristatus, according to Hoffman 2 , the sacral nerve 

 is formed by one root preaxiad and two postaxiad of the transverse processes joining the 

 ilium. Dr. J. G. de Man 3 agrees with this representation, save that he places all the 

 roots one vertebra more preaxiad. We found, in Triton cristatus (PL LXVI. fig. 6), 

 the same conditions as those described by Dr. de Man ; but there was an interesting 

 difference between the two sides of the individual examined, inasmuch as there was a 

 lumbo-sacral nerve (12) only on one side, so that the sciatic had two roots (21 and 30) 

 on one side and three upon the other. 



According to Professor Gegenbaur 4 , Salamandra maculosa 

 has three roots to its sacral plexus — (1) a delicate branch from 

 the nerve coming out preaxially to the large transverse pro- 

 cess ; (2) one large root formed by the whole of the nerve, 

 i. e. coming out postaxially to the large transverse process ; 

 and (3), a delicate branch from the nerve next postaxiad. 

 Thus Gegenbaur agrees with Hoffman and differs from 

 Dr. de Man. 



We found that a specimen (woodcut, fig. 6) of this species, 

 dissected by us, agreed as to its sacral roots with the obser- 

 vations recorded by Dr. de Man and figured by him in his 

 Table vii. fig. 4 ; but the branch connecting the second post- 

 sacral (9) nerve with the next postaxial nerve (12) appeared 

 to us to be rather formed of fibres going preaxiad to the 



crural nerve (15) than of fibres going thence postaxiad to the sacral (33). If we were 

 right in this view, the sacral nerve had but two roots, one issuing preaxiad (12) and the 

 other postaxiad (30) to the ilium-joining vertebra. Moreover, in our specimen, a branch 

 from the third preaxial nerve (2) joined, but very slightly so, the lumbar plexus on one 

 side, while on the other side it approximated to, but did not join, that plexus, and then 

 went on its way. 



In the tailless Batrachia, the sciatic nerve appears, according to Hoffman 5 , to be 



1 L. c. p. 149, fig. 1. 2 L. c. p. 149, fig. 2. 



3 " Myologie comparative de l'extremite posterieure chez les Amphibies," Niederlandisch.es Archiv, ii. p. 58. 



4 L. c. p. 200. 5 L. c. pp. 156, 157, figs. 3, 4. 



Lumho-sacro-caudal vertebra? and 

 nerves of Salamandra maculosa. 

 The lettering and numbers 

 agree with those of figures in 

 the Plates and as described in 

 the text. 



