348 F. L. LANDACRE 



Gasserian and geniculate ganglia from which it derives its two 

 components lie side by side and their anterior ends from which 

 the nerve arises are intimately in contact when it can first be de- 

 tected. The arrangement of the roots of the geniculate, later- 

 alis Vllth and auditory ganglia are shown in figs. 36 to 39. They 

 are all quite distinct and can be followed to the point of contact 

 with the medulla. 



As mentioned above, from this time on the components of the 

 Vth and Vllth ganglionic complex become more intimately fused 

 so that it is not surprising that nerve trunks which are at first 

 undoubtedly pure trunks, i.e., contain only one component, later 

 become mixed and contain two or more components. The con- 

 tiguity of the ganglionic masses furnishes a basis for the mixing. 

 Those components which are not found in the nerve at first must 

 grow into it later. They are unquestionably there in the adult 

 and not there in the embryo. The geniculate ganglion wedged 

 in between the Gasserian and lateralis Vllth ganglia is in a par- 

 ticularly favorable position to send its fibres into nerves derived 

 primarily from other ganglia. This has gone so far in Ameiurus 

 that 12 out of 14 of the chief nerves coming from the acustico- 

 facialis complex contain visceral fibers, as compared with five 

 in Gadus and Menidia. 



There are, at least, three methods by which nerves become 

 mixed. The first is illustrated by the maxillary and mandibular 

 trunks which arise some distance from the ganglion, after the fu- 

 sion of two pure strands, the supero-lateral which is pure general 

 cutaneous and the infero-mesial which is pure visceral. These 

 pure strands after coming into contact break up into two mixed 

 nerves, the maxillary and the mandibular. A second method by 

 which nerve trunks become mixed is illustrated by the hyomandib- 

 ular which is at first a pure lateralis nerve but later becomes mixed 

 by having general cutaneous and visceral fibres grow into it from 

 their respective ganglia. A third method is illustrated by the 

 rami oph. sup. V and VII which, owing to the contiguity of its gan- 

 glia, the Gasserian and geniculate, seems to be mixed from the 

 first, the roots growing out from the ganglia in contact with each 

 other. 



