496 PHYSIOLOGICAL SERIK<. 



MAMMALIA. 



MONOTREMATA. 



D. 772. The brain and spinal cord of a Duck-billed Platypus 

 (OraUhorkyncku* jHinido.rns) exposed from above. The 

 cord extends into the tail, gradually diminishing in si/.e as 

 it passes backvvaids. The brachial and crural enlargements 

 are but slightly marked. 0. C. 1358 A. 



D. 773. A similar specimen of the brain and spinal cord of a 

 Spiny Ant-eater (Tacliyglossus [Echidna] aculeatus). The 

 cord is remarkably stout and terminates in the thoracic 

 region, at a point about a third of the distance from the 

 brachial plexus to the sacrum. From the medulla to 

 within two centimetres of its termination it is of great 

 size and of about equal calibre, but then rapidly comes 

 to a point and ends in a fihmi terminals amidst the bundle 

 of backwardly directed nerve-roots that constitutes the 

 cauda equina. The branching rootlets of the sensory roots 

 of the spinal nerves are well shown, particularly in the 

 brachial region. There is no marked swelling of the cord 

 at this point. O.C. litfSu. 



INSECTIVORA. 



D. 774. A Hedgehog ( AV///'/<r//.< i-nro/urn*) with the brain and 

 spinal cord exposed from above. The spinal cord, as in 

 Tachyylosws, is remarkably short. It extends, of abottl tin- 

 same calibre, from the medulla Jo the level of the third rib. 

 and from this point rapidly diminishes in si/e, until on a 

 level with the fifth rib it is replaced by a delicate terminal 

 lilament, \vhich forms the central strand of the cauda 

 equina. 



In thi^ specimen the brachial plexuses have been di-sccted. 



O.C. 1372B. 



