go JouRNAL OF COMPARATIVE NEUROLOGY. 
uniformly active physiological condition. Commissural neu- 
rones doubtless have a not unimportant place in the economy 
of this region of the brain, into which so many impulses sweep 
through afferent nerve-fibres to great vital centres. The chain- 
ing together of the opposite halves is precisely what we should 
expect to find under such conditions, and the mechanism is pro- 
vided by the commissural neurones just described. 
4. Lobus Vagi and Fasctculus Communis. 
The lobus vagi is the terminal station for the communis 
fibres, components of the VII, IX, and X nerves. Its general 
morphology has been outlined in Subsection 1. 
The structure of the lobus vagi embraces a narrow zone 
next to the limitans interna occupied chiefly by nerve-fibres ; 
and a deeper part in which there are both neurones and term- 
inating fibres. The course of the nerve-fibres will be consid- 
ered later. 
a. Neurones of the Lobus Vagz.—The constituent neurones 
of the lobus vagi are many in number and closely crowded. 
They. are comparatively small in size, and are referable to type 
II of Gotct. The external morphology of a neurone is shown 
in Fig. 4. 
The shape of the cell-body ranges from almost triangular 
to broadly oval. The axone may emerge directly from the 
cell-body, or it may spring from one of the larger dendrites. It 
pursues an irregular course away from the limitans interna into 
the deeper levels of nervous matter. Before proceeding far, it 
breaks up into a widely-spread arborization such as is character- 
istic for neurones of this type. I believe, from the course of 
the axones, that they constitute a means for transmitting impres- 
sions to the viscero-motor nucleus ; see Subsection 5. 
The dendrites are three or fourin number. They are quite 
stout near their origin, they taper gradually, and they do not 
become very fine at their terminations. Their morphology is 
simple, since there are only one or two branchings at most. 
Their lengths may be as great as that of the axone, and so the 
dendrites from all of the neurones here interlace to form a veri- 
