THE NERVES OF THE BRANCHIENCEPHALON. 



103 



The Haemal Nerves (Figs. 59 and 70), arise from the anterior margin of 

 the neuromere and extend outward over the neural surface of the abdominal 

 muscles. They divide into five principal branches; one goes to the enteron, one 

 to the longitudinal abdominal muscles, one to the branchio-thoracic muscles, 

 one to the heart, and one to the integument. 



Cran 



Fig. 76.— Side view of the brain, endooranium, alimentary canal, and principal vascular channels in Limulus; semi 



diagrammatic. 

 Fig. 77- — Same, showing the relation of the compound branchio-thoracic, or hypobranchial nerve to the hsemal 



nerves of the vagus and branchial-neuromeres. Semi-diagrammatic. 

 Fig. 78. — Same, showing the relation of the segmental cardiac nerves, s.c.M.6-13, to the heart and to the vagus and 



branchial neuromeres. Semi-diagrammatic. 



The Enteric Nerves.— In Limulus, the enteric nerves are intimately associated 

 with the nerves to the longitudinal abdominal and haemo-neural muscles. The 

 enteric nerves form a plexus which covers the entire mesenteron and the plexus 

 is united with the roots of all the hasmal nerves, from the sixth to the sixteenth, by 

 paired rami communicantes. (Fig. 59 f'^) Those from the sixth and seventh 

 neuromeres pass through the foramina in the posterior lateral wall of the 

 endocranium. (Figs. 59^"* and 218.) 



