THE CRANIAL GANGLIA IN AMEIURUS 347 



trunks derived from these ganglia are found to contain only gen- 

 eral cutaneous or communis or lateralis fibres. 



Fig. 31 is taken through the origin of the trunk of the Gasserian 

 ganglion, and fig. 32 just anterior to the point where the trunk 

 of the geniculate ganglion leaves the ganglion, and consequently 

 lies between the trunks of the Gasserian and geniculate ganglia. 

 These two trunks are entirely separate not only at their point of 

 origin but throughout their whole course at this time. They form 

 the supero-lateral and infero-mesial strands respectively of Wright 

 ('84 b) . These combine and later separate to give rise to the maxil- 

 lary and mandibular trunks which are mixed, containing general 

 cutaneous, visceral, and lateralis components. Herrick ('01, p. 

 183) could not determine positively that these two strands were 

 pure but there can be no doubt that they are pure at this stage and 

 that the supero-lateral strand contains fibres from the Gasserian 

 ganglion only and that the infero-mesial strand contains fibres 

 from the geniculate ganglion only. Further, the roots are not yet 

 in contact at any point nor do they contain lateralis fibres as yet. 



Figs. 33 and 34 are taken through the root of the Gasserian 

 ganglion and show that the root is no less distinct than the trunk. 

 The dorso-lateral lateralis Vllth also appears in these sections. 

 The roots of the geniculate and Gasserian ganglia are separated 

 by 15 sections, while the trunks at this stage are six sections apart. 

 The overlapping of the ganglia finally brings the trunks into the 

 same plane but even then there can be no doubt that they are 

 derived separately from their respective ganglia. 



Fig. 35 is taken through the origin of the hyomandibular nerve 

 (T. V. L. VII) which is at this time a pure lateralis nerve derived 

 from the ventral lateralis Vllth ganglion (V. L. VII). This 

 nerve later contains in the adult small strands of general cutaneous 

 and visceral fibres (Herrick, '01) but is at first a pure lateralis 

 nerve. The ramus oph. sup. VII is in the adult a pure lateralis 

 nerve. In this stage it can be detected as a forward extension 

 of the anterior end of the dorsal lateralis Vllth ganglion but it is 

 only faintly fibrillated. The ramus oph. sup. V, I cannot detect 

 at this stage but it is probably mixed at an early stage, since the 



