CHAP. IV.] 



SPINAL NERVES : BRADYPODID^. 



141 



(von Jhering, I. c. p. 182, pi. iv. tig. 2). Descriptions and diagrams 

 of similar cases are given throughout the work, but as some of them 

 represent specimens described by others (e.g. Struthers and Rosen- 

 berg) originally without diagrams, it is difficult to know how far the 

 accounts given are schematic. For this reason reference to the original 

 work must be made. 



Bradypodidae. Brachial plexus. As examples of normal differ- 

 ences the Sloths are especially interesting, but unfortunately an 

 extended investigation of the nerves in several individuals has not 

 been made. The results found by Solger relate to one specimen of 

 B. tridactylus and one of C. didactylus. The latter was a perfect 

 specimen, but the former had been partially dissected and the details 

 of the nerves were largely imperfect. The Cholcapus was a specimen 

 with seven cervicals, and the Bradypus had nine, the last bearing rudi- 



[ 



n 



Fig. 15. Diagrams shewing the composition of the brachial plexus in 

 I. a Cholapus, II. a Brady-pus. r 1 — v 11 , the vertebrae. IV, VII, X, XII fourth, 

 seventh, tenth and twelfth cervical nerves. A, dorsal cord. B, ventral cord. 

 a, phrenic, b, dorsalis scapula;, c, suprascapular, d, subscapular. 



mentary ribs. As the figure shews (Fig. 15), there was a close but not 

 a perfect resemblance between the composition of the plexus in the 

 two cases, that of Bradypus being in nearly each case two roots lower 

 than that in Cholcepus. In the latter the IVth nerve gave a branch 

 to the Vth, but whether in Bradypus the Vlth gave a branch to the 

 Vllth was not determined with certainty owing to the condition 

 of the specimen. [For details see original paper] Solger, B., Morph. 

 Jahrb., 1875, i. p. 199, PI. vi. 



One more case may be given in illustration of the kind of 

 difference which normal forms may present. 



74. Pipa (the Surinam Toad). In the majority of the Batrachia, the 

 most anterior pair of spinal nerves leaves the vertebral column between 

 the first and second vertebrae, no sub-occipital being present. The 



