94 OSBORN. [Vor. I. 
EXPLANATION OF PLATE V. 
Fics. 10 To 18. A series of transverse sections through the medulla oblongata of 
Cryptobranchus alleghaniensis, from the exit of the 12th pair (XI.) to the exit of 
the 6th pair, enlarged about forty diameters. For the sake of clearness only a few 
cells of each nucleus are represented, and these are drawn to scale. Most of the 
sensory and motor cells of the Cez¢ra/ region are also omitted. The cell area is 
represented in dark gray. The contours of the tracts are usually well defined, but 
have been exaggerated in several figures. The level of the transaction represented 
by each of these figures is indicated in the diagram, Fig. 21 (— f. 10— f. 18). 
Fic. 19. Sagittal section through the tectum opticum (of/) and cerebellum of 
Cryptobranchus. This shows the posterior portion of the great trigeminal nucleus; 
the small nucleus of cells in the cerebellum, cd/z; the decussating cerebellar tracts, 
chit; and the descending trigeminus, 574. 19a represents the cells of the tri- 
geminal nucleus enlarged. 
Fics. 20 AND 20a. Vertical and horizontal sections through the oculo-motor 
nucleus, as seen under a Zeiss D; camera drawing. 
Fic. 21. Diagram of the cranial nerve nuclei of Cryptobranchus, as reconstructed 
from transverse and horizontal sections. The relative location of the 3d—6th nuclei, 
posterior commissure, Meynert’s bundle, the main exits of the nerves and the pos- 
terior longitudinal fasciculus are all determined with the camera. The nuclei of the 
5th-10th pairs are reconstructed from transverse sections. They overlap each other 
less closely than in nature. The sezsorvy nuclei are distinguished by oblique lines; 
the ofoy nuclei by transverse lines; the pale ganglion nucleus of the Auditory by 
crossed lines. The external row, 5, 7,9, are the dorsal sensory nuclei. The 
internal row, 5, 9, 10, are the ventral motor nuclei. The external intermediate, 
7, 9, are the doubtful lateral motor nuclei, adjoining 8 and f the lateral 
sensory nuclei. 
The fasciculus communis /,//”’ is represented in gray to indicate that it is 
apparently forming new bundles from a continuous sensory nucleus. 
The dotted lines represent the descending, 7.e. encephalic, tracts. The heavy lines, 
the descending trigeminus and the posterior longitudinal fasciculus. The pale lines, 
the tracts springing from the special nuclei. 
