PHYSIOLOGY OF THE INVERTEBRATE HEART. 151 



cardiac nerves take their origin dorsally on the thoracic ganglion 

 close to the origin of the recurrent cutaneous nerve, the nerve to 

 the third maxilliped, and the nerve to the first ambulatory 

 appendage respectively. The nerves that reach the heart in the 

 trunk of the recurrent cutaneous nerve, that is, the anterior pair 

 of cardiac nerves, were found to be inhibitory in function, the two 

 posterior pairs to be accelerator. Bottazzi (1901) has confirmed 

 the results of Jolyet and Viallanes and Connant and Clarke as 

 regards the presence in the thoracic ganglion of both accelerator 

 and inhibitory centers to the heart. 



Nerve cells in the walls of the crustacean heart have been de- 

 scribed by Berger (1876), Deszo (1878), Young (1878), Dogiel 

 (1877, 1894), Plateau (1880), and Pagoschwa (1890). Deszo 

 states that the ganglion cells are especially abundant in the pos- 

 terior half of the dorsal wall. 



The results of Jolyet and Viallanes and of Connant and Clarke 

 on the crab appeared to me so conclusive that I did not take the 

 time to work out the cardiac nerves in the available material of 

 this group {Cancer, Bracliynotus, Epialtus], but instead I confined 

 the anatomical work to the large spiny lobster (Palinurus}, and it 

 may be stated at the outset that the cardiac nerves in this decapod 

 have nearly the same relations as given by Connant and Clarke 

 for Callincctes. The dorsal side of the large thoracic ganglion 

 gives rise to six pairs of small nerves (PI. VIII., Fig. 22, I to 6). 

 The anterior pair takes its origin near the roots of the nerves to 

 the third maxilliped. On leaving the ganglion the nerves run 

 alongside (but not in the same sheath as) the recurrent cutaneous 

 nerves for some distance in an anterior, lateral and dorsal direc- 

 tion. The recurrent nerves turn posteriorly after passing around 

 the anterior processes of the endophragmal skeleton, but their 

 smaller companions (i) pass through the foramina between the 

 two anterior endostermites. Reaching the inner surface of the 

 endoskeleton at this point the nerves take a dorso-lateral direc- 

 tion ventral to the anterior flexor muscles of the abdomen, and 

 on reaching the point of attachment of the extensor muscles the 

 nerves pass posteriorly on these muscles and finally ramify in 

 them posterior to the level of the pericardial cavity. At the level 

 of the pericardial cavity each nerve gives off a branch (7) to the 



