rv. 



OF RANA PIPIENS. 



47 



Fig. 4. 



elusive ; at its anterior extremity, no filament was traced to the motor communis, 

 though analogy would lead us to expect one ; nor at the other extremity was any 



traced to the coccygeal pair. The filament from the 

 ganglion of the trigeminus to the vagus is very mi- 

 nute, and, as will be seen by reference to the figure, 

 no sympathetic ganglion is developed upon it. Pre- 

 cisely similar conditions exist, according to Fischer, 

 in Bomhinator igneiis, Pelobates fiiscus, and Hi/Ia 

 arhorea ; also, according to Vogt, in Bufo pantheri- 

 nus. From the posterior extremity of the vagal 

 ganglion, the nerve extends backwards as far as 

 the fourth dorsal, receiving filaments from the hy- 

 poglossal, brachial, and the two succeeding spinal 

 nerves, and Avhere each of these filaments joins the 

 sympathetic trunk, a distinct ganglion is formed. 

 After it receives its fibres from the fourth spinal 

 nerve, it is enlarged, leaves the side of the verte- 

 bral column, and forms, with the nerve from the 

 opposite side, a plexus around the mesenteric artery, 

 from which it is distributed to the spleen, stomach, 

 and intestines. 



The branches of the fifth and sixth pairs unite 

 and form a ganglion, from which a small branch 

 goes to the splanchnic plexus, and another back- 

 wards to the ganglion of the next nerve (seventh), 

 which is the first of the crural or lumbar pairs ; 

 this last ganglion in turn sends a branch back 

 to the ganglia of the eighth and ninth pairs, 

 e, e, e. The filaments given off from the group 

 just mentioned are distributed almost entirely 

 to the kidneys and neighboring viscera, follow- 

 ing the course of the bloodvessels which ramify 

 upon them. 



It is seldom that we have a more favorable op- 

 portunity oftered for studying the minute structure 

 of the ganglia than in the sympathetic system of 

 Frogs, where they are both small and transparent. I have not been able to deter- 

 mine any thing diff"erent from what was previously known with regard to their 

 minute structure. Fig. 10, Plate II. represents the ganglion just behind the third 

 spinal nerve ; a, 6 is the principal trunk of the nerve ; c is the sympathetic 

 branch ; d, d, the sympathetic trunk in front of and behind the ganglion. Some of 

 the fibres of the sympathetic pass through the ganglion without separating ; others, 

 leave the principal fasciculus, and become more or less mixed up with the nerve 

 cells entering into the composition of the ganglion. 



V. Trigeminus. 



VI. Auditory nerve. 

 VII. Vagus. 



a and 6. Right and left aortas at their union 



c. Mesenteric artery. 



d. Descending aorta. 



e. e. e. Renal and genital ganglia. 



The branch c divides into two 



