THE NERVOUS SYSTEM. 185 



the rami communicant es, seeing that individual fibres of them, 

 actually join peripherally the spinal nerves; and the rami car- 

 diaci, pidmonales, &c. Other branches in the parenchyma of 

 the organs become so fine, that it is impossible to trace them. 

 What has been as yet established respecting their ultimate 

 course, is as follows: 1. Divisions occur in the branches and 

 terminal ramifications of the sympathetic, as in the nerves of the 

 spleen, the Pacinian bodies in the mesentery, in the nerves 

 accompanying the mesenteric vessels in the Frog, in those 

 which exist temporarily in the uterus of the Rodentia, of the 

 lungs and stomach of the Frog and Rabbit, of the dura mater 

 on the meningeal arteries, in branches of the sympathetic of the 

 Sturgeon, in the cardiac nerves of the Amphibia, and in those of 

 the urinary bladder in the Rabbit and Mouse. 2. There are 

 free terminations of the nerves, as in the Pacinian bodies and 

 on the mesenteric vessels in the Frog. 3. The thicker fibres of 

 the sympathetic ultimately so decrease in size, as to become 

 of the fine kind ; as may be readily seen in the rami intestinales, 

 lienales, and hepatici, which, indeed, even in the interior of the 

 organs in question, contain some coarser nerve-fibres, but ulti- 

 mately lose them. The actual terminations, however, in the 

 organs themselves, in the heart, lungs, stomach, intestine, 

 kidneys, spleen, liver, uterus, &c, are as yet quite unknown; 

 although from the impossibility of finding any dark-bordered 

 fibres in the ultimate ramifications of these nerves, it may be 

 supposed that they terminate, almost everywhere, in non- 

 medullated, embryonic fibres. In fact, I have, at all events 

 hitherto, in vain endeavoured to find a trace of them. Schaffner 

 says, that in the heart of Bombinator he has seen the passage 

 of the dark-bordered fibres into pale, anastomosing fibrils of 

 the finest kind, whilst Pappenheim (1. c.) describes loops in the 

 nerves of the kidney. 



[As regards the nature of the " fibres of Remak," most, re- 

 cent observers incline to the opinion first advanced by Valentin 

 ('Repert./ 1838, p. 72; Muller's 'Archiv/ 1839, p. 107), that 

 they are not nerve-fibres at all, but to be referred to the con- 

 nective tissue of the nerves ; whilst Remak still thinks himself 

 obliged to adhere to his previous opinion, that they are, or may 

 be, in part at least, nerve-fibres (' Darmnervensyst./ p. 30). As 



