( 92 ) 



cervicale, which, as in Ecliidiia, is situated close above the Arteria 

 subclavia. 



The communication between the ganglion cervicale and the 

 ganglion stellatnm is formed in Echidna by two nervestems, which 

 form an Ansa Vieiissenii I'onnd the Arteria subclavia ; in Ornitho- 

 rhynchus I only found one nervestem passing backwards round this 

 artery. In both, the nei've that passes at the back of the artery is 

 connected with the rami viscerales of the sixth and seventh cervical 

 nerves, while that of the eighth cervical nerve passes directl}^ into the 

 ganglion stellatum. This ganglion also receives the rami viscerales 

 of the first and second thoracic nerves. (The latter in Echidna partly). 

 The ganglion cervicale sends out some nerve branches to tiie heart, 

 close to rami cardiaci of the vagus nerve (Fig. 1 and 2 r. c). In 

 Echidna these branches are also sent out from the anterior nervestem 

 of the Ansa Vieussenii. 



The cervical sympathetic system in Monotremes differs from that 

 of the placental mammals not only by the composition and arrange- 

 ment of the cervical ganglia, but also in the nervus vertebralis, 

 which is wanting in Monotremes ; in both Echidna and Ornitho- 

 rhynciius the rami viscerales of the cervical nerves run extravertebral. 

 If mechanical influences be the cause of the origin of the vertebral 

 ner\e (cordon apophyso-vertrébrale of Thebault '), it is important to 

 point out the peculiarity of the cervical vertebrae in Monotremes, 

 in which the rudiments of the ribs only confuse at a very late stage 

 of development with the transverse processus of the vertebrae. 



The visceral branches of the first and second thoracic nerves run 

 to the gajiglion stellatum; the third till twelfth intercostal nerves 

 included are connected by very short rami viscerales with the top 

 of triangular ganglia, situated in the spatia intercostalia. 



From the seventh unto the eleventh spatium intercostale the sym- 

 pathetic chord of Echidna is divided into two chords that run parallel, 

 the lateral of which is much smaller than the medial one. 



From the latter there goes a nerve in caudo-medial direction, 

 which I could follow as far as the aorta. The rami viscerales of the 

 ninth and tenth thoracic ner\es of Ornithorhynchus divide into two 

 rami and go to two sequent ganglia. With both animals the sym- 

 pathetic chord, where it receixes the ramus communicans of the 

 thirteenth thoracic nerve, makes a curve in medial direction and 

 penetrates the diaphragm in front of the vertebral column. 



1) Thébault. V. Etude sui' les rapports qui existent entre le système pneumo- 

 gaslrique et synipatliique chez les Oiseaux. 

 Annales des Sciences naturelles. Série 8. Tome VI, p. 1. 



