952 THE LUMBAR ENLARGEMENT OF THE SPINAL CORD. 
Explanation of the Plates. 
Fig. 1. Transverse section representing part of the anterior cornu, from the lumbar 
enlargement of the rabbit. a, a, a’, bundles of fibres belonging to the anterior roots; 
in the bundle marked a’ two cell processes can be traced to the outer boundary of the 
cord; b, b, outer boundary of the white substance; c, c, boundary of gray substance ; 
d, d, cell connectives of the short, thick variety; e, a longer cell connective. Drawn 
by the camera lucida, with one of Nachet’s microscopes, from a preparation magnified 
160 diameters; the scale is in hundredths of a millimetre. 
Fig. 2. Group of cells from the anterior cornu of the sheep, connected with the 
radiating bundles from which the longitudinal fibres of the white substance are de- 
rived. a,a,a, radiating bundles; B, a large cell, sending its processes, b, b, b, into four 
different bundles; c, a process passing forward towards the anterior roots; d, d, long 
cell connectives. Figs. 2 to 7, inclusive, were drawn by the camera lucida, with eye- 
piece No. 1, objective 45, of one of Smith and Decke first-class instruments, giving a 
power of 120 diameters; the scales affixed express thousandths of an inch. This and 
the following figures are all from the lumbar enlargement. 
Fig. 3. Group of cells from the anterior cornu of the sheep, connected with the 
anterior roots at A; B, fibres radiating to the side of the cornu; C, fibres passing to 
the interior of the cornu. This figure represents a somewhat deeply lying group 
of cells as seen in a transverse section. 
Fig. 4. Group of cells connected with the anterior roots, as seen in a transverse 
section, from the anterior cornu of the sheep. A, entrance of the anterior roots into 
the cornu; b, b, b, b, cells connected by long, slender processes with the anterior roots ; 
c, €, boundary of the cornu. In this figure almost every variety of cell connection may 
be seen, with bundles of fibres crossing in every direction. 
Fig. 5. Group of cells connected with the anterior roots, from a longitudinal sec- 
tion through the anterior cornu of the sheep. A, white substance; B, gray substance ; 
a, a, cell processes passing upwards to form the ascending fibres of the white substance ; 
a’, a’, bundles of ascending fibres; b,b, cell processes passing into the anterior roots; 
b’, V, anterior root bundles; c, c, descending fibres and bundles (c. Different forms 
of cell anastomosis may also be observed in this figure. 
Fig. 6. Longitudinal section through the posterior cornu of the calf, drawn just 
inside the gelatinous substance, on a plane with the entrance of the posterior roots. 
a, a, a, ascending bundles of fibres, longitudinal columns of the cornua, connected on the 
one side with the posterior roots, and on the other with cells which belong to the pos- 
