The Cranial Nerve Components of Petromyzon. 183 
short distance, then goes to join the eoarse fibered »hypoglossus« 
trunk in 1010. 
Spinal ventral 13 arises at 975. Its ventral ramus could not 
be completely traced. 
Spinal dorsal 13 arises at 1001, has its ganglion in the same 
plane and its ventral ramus joins the »hypoglossus« trunk in 1040. 
Spinal ventral 14 arises in 1026 and its ventral ramus enters 
the »hypoglossus« in the same sections with the 15!" dorsal. 
Spinal dorsal 14 has its root in 1055, spinal ventral 15 has its 
root in 1073, and spinal dorsal 15 has its root in 1100. None of 
these were completely traced out. The ventral ramus of sp.d. 14 
was traced far enough to show a probability of its meeting with 
the »hypoglossus«. 
Summary and Conelusions. 
An extended discussion of the literature of the eranial nerves is 
quite unnecessary after the many papers on nerve components which 
- have appeared in recent years. For such general discussions the 
papers by STRONG, COLE, HERRICK, the writer, and others should be 
referred to. It will be möre profitable in the present connection to 
give a brief review of the several nerve components and to point 
out those facts which are significant for our general view of nerve 
components and of head morphology. 
General Cutaneous System. 
The general eutaneous fibers form components of the profundus, 
trigeminus, facialis, glossopharyngeus and each of the branchial 
nerves connected with the vagus trunk. T’'hese components have for 
their center the whole length of the eutaneous sensory column from 
the dorsal horn of the cord to and ineluding the cerebellum. A part 
of the tubereulum acusticum is free from general cutaneous fibers. 
The N. profundus eombines in a single supra-orbital trunk its 
proper general cutaneous fibers with a component from the trigeminus 
ganglion and the supra-orbital neuromast component. 
The formation of a single trunk is perhaps due to the erowding 
from the large buccal funnel, as is also the high dorsal position of 
the infraorbital row of pit organs. The profundus also contains a 
small number of neuromast fibers which form a small dorsal ramus 
from the ganglion, supplying the two pit organs on the dorsal sur- 
face of the head. These fibers are probably to be identified with 
13* 
