CENTRAL RELATIONS OF COMPONENTS. 5 I 



"its common relations to a number of the cranial nerves." 

 In the Amphibia the fasciculus communis receives most 

 of the root fibres belonging to what I have called the com- 

 munis system. These enter with the VII, IX and X 

 roots. The fasciculus is a tolerably uniform tract which, 

 after receiving the root fibres above mentioned, continues 

 into the spinal cord uninterruptedly as far as the first 

 spinal nerve, being accompanied for almost its entire 

 length by a strand of nerve cells which constitute a ter- 

 minal nucleus for its fibres, the spinal nucleus of the 

 fasciculus communis. This tract is the "Radix bulbo- 

 spinalis Vagi et Glossopharyngei " of Edinger ('96, p. 84). 



In the fishes, however, the greater part of the fibres of 

 this system enter the oblongata through the chief vagus 

 root and pass directly to their terminal nucleus in the 

 lobus vagi without entering the fasciculus communis in 

 the original sense of that term. The chief root of the 

 vagus is in the fishes (and doubtless in the higher forms 

 also) a complex of at least three kinds of fibres: (i) 

 Sensory fibres from the general visceral surfaces without 

 specialized end-organs. (2) Sensory fibres from taste 

 buds in the mouth and from similar terminal buds vari- 

 ously scattered over the outer surface of the body. It is 

 generally assumed that these two classes of buds have a 

 common origin, as well as a common structure and inner- 

 vation. They must be sharply distinguished from the 

 neuromasts, or organs of the lateral line (nerve hillocks of 

 Merkel), which belong to a distinct system. (3) General 

 cutaneous fibres from the outer skin. The latter category 

 and all motor fibres are excluded from the communis 

 system. 



In the communis system, then, there are represented 

 two types of fibres, the general visceral and the taste bud 



