Houser, The Neurones of a Selachan. 93 
5. The Viscero-Motor Nucleus. 
The adoption in this paper of the name w7scero-motor nu- 
cleus expresses the need for a general term which shall include 
all members of the morphologically continuous column of cells 
giving origin to the motor fibres of the V, VII, IX, and X 
nerves. This nucleus is the continuation into the oblongata 
of the paracentral nucleus of Onur and CoLLins (’98), and the 
components having their origin here innervate viscera. 
The nucleus is composed of quite large neurones. The 
only larger ones in the oblongata are the gigantic tract-neurones 
described in Subsection 3, a. The cells are arranged in a com- 
pact cluster, as seen in transverse section, and this is traversed 
during a part of its course by the fasciculus communis. Fig. 
2, v. m. n., illustrates the disposition of the neurones and their 
characteristic forms. 
The cell-body has its form influenced by the number of 
its dendrites, ranging from triangular to stellate. The dendrites 
are always several in number. They are massive processes, 
often arising through such wide bases that it is difficult to say 
where the line of demarcation between dendrite and cell-body 
should be drawn. The dendrites branch freely, and the close- 
ness with which the neurones are arranged gives, therefore, a 
most complicated tangle of interlacing branches. 
The internal organization of a viscero-motor neurone is 
represented in Fig. 47. The nucleus is central, or only slightly 
eccentric, and it has an evenly rounded contour. The nucle- 
olus is large; there is rarely a subsidiary nucleolus. The nu- 
clear reticulum has a coarse mesh which exhibits great clots or 
lumps of chromatin at the points of intersection. 
The cytoplasm. contains tigroid-bodies of various sizes. 
The largest ‘masses lie in the field of the nucleus. The ones 
next to the nuclear membrane may assume the form of nuclear 
caps. At the periphery of the cell, the prevailing form of 
tigroid is much elongated. It lies parallel with the margin of 
the cell. Tigroid masses are continued far along the dendrites, 
