80 JouRNAL oF CoMPARATIVE NEUROLOGY. 
tained, the sections were transferred to tap-water. Thorough 
washing at this stage is necessary to prevent fading of the stain, 
and the slight alkalinity of ordinary tap-water appears to be a 
factor aiding in jits preservation. 
4. The Chloride of Vanadium Method. 
The technique required for staining with the chloride of 
vanadium method of Wo tTERs (’90) is somewhat troublesome, 
but the results, when obtained, certainly justify the means. 
Nerve-cells, axis-cylinders, ependyma, and neuroglia are all de- 
fined in one andthe same section. No other method known to 
me gives so comprehensive a picture for general study. Its sole 
value lies, however, in the purely general scope of the results. 
It is hardly necessary to give a description of the process 
here, since its essentials are outlined in LEE (1900, p. 410). 
Section IV. THE OBLONGATA. 
z. General Morphology of the Oblongata. 
In Mustelus, the transition of the architecture of the spinal 
cord into that of the oblongata is traceable with a degree of 
definiteness which rarely obtains in other animals. It is there- 
fore possible to contribute toward the solution of certain prob- 
lems which vex the study of this highly specialized region of 
the mammalian brain. Only an introductory survey of the 
entire field will be presented here, leaving the development of 
details and the consideration of special questions to the follow- 
ing subsections. 
As the canalis centralis widens into the fourth ventricle, 
the several structures of the cord lateral to it are pushed into 
more and more widely divergent positions, retaining, however, 
essentially the same mutual relations to each other. Concomi- 
tant with this divergence, the dorsal ependyma becomes broad- 
ened to form the morphological roof of the fourth ventricle 
(Bigy)2; 2. ¢. p.). 
In approaching the oblongata, the ventral cornua are en- 
croached upon more and more by commissural fibres until, just 
above the level of the first spinal nerve, the mammalian hypo- 
