I 54 A. J. CARLSON. 



nerves do make such a connection, as I have represented in Fig. 

 24. This is also borne out by the physiological experiments. 



From the dorsal side of the brain corresponding to each pair of 

 nerves to the ambulatory appendages is given off a pair of nerves 

 which take a dorsal direction to innervate the integument, the 

 viscera, and dorsal musculatures. These nerves are evidently 

 homologous to the nerves occupying a similar relation to the 

 thoracic ganglion in Palimtriis (Fig. 22, I 6). The anterior 

 pair of nerves from each abdominal ganglion takes a similar 

 course and make connections similar to those from the dorsal 

 side of the brain. As these nerves go to innervate organs lying 

 dorsal or haemal to the level of the central nervous system, Patten 

 and Redenbaugh call them haemal nerves in contradistinction to 

 the nerves to the ambulatory appendages and the gills which are 

 designated as neural nerves. 



The haemal nerves from the abdominal chain of ganglia (Fig. 

 2j, 913) takes a dorsal and posterior direction and after giving 

 off their fibers to the intestine and the integument, penetrate the 

 pericardial cavity, each sending a small fillament along the dorsal 

 wall of the pericardial cavity to unite with the nerve-cord on the 

 heart approximately opposite the fourth to the eight pairs of ostia. 

 These cardiac branches are, with the exception of those from the 

 ninth and the tenth nerves, so tiny that they are not readily made 

 out in the living tissue. Prior to the entrance of these nerves into 

 the dorsal pericardium to connect with the nerve-cord each nerve 

 sends a communicating branch to the nerve which runs parallel 

 to the heart in either angle of the pericardial cavity. These nerves 

 are designated as pericardial nerves by Patten and Redenbaugh. 



Of the haemal nerves given off from the brain the only ones 

 that I was able to trace to the heart are the last two pairs (Fig. 

 -5. 7> 8). The cardiac branches of these nerves unite in one 

 common trunk before reaching the pericardial cavity. The 

 main branches of this large nerve go to make up the pericar- 

 dial nerves and to innervate the large inter-tergal muscle, which 

 lies dorsal and lateral to the heart in this region. The branches 

 that pass to the epidermis in the median line connect with the 

 nerve-cord on the heart in the manner shown in Fig. 24. There 

 is considerable individual variations as to the exact place of con- 



