158 JULIA WORTHINGTON. 
caudad of the apex there is a semi-circular band, whose cut 
ends point forward, sculptured in slight relief (fig. 2). This 
ring consists of the two bundles of Meynert and their second 
decussation. A longitudinal depression, not as clean cut as 
the median one, divides each side of the ventral surface of 
the medulla into approximately equal parts, so that the ven- 
tral surface consists of four longitudinal divisions—two lateral 
and two median. In the caudal end of the median divisions 
are continued the ventral fibre-tracts of the spinal cord; in 
the lateral divisions are lodged the lateral motor columns of 
the medulla. 
Turning now to the dorsal surface, we see that the raised 
dorsal part of the spinal cord expands into a large Y, whose 
thick arms compose almost the entire dorsal surface of the 
medulla, not separating until more than half-way to their 
anterior end, where they admit between them the lobes of 
the cerebellum (fig. 1). ‘’hree distinct divisions are sculp- 
tured on the arms of the Y :—(1) ‘The great strands that run 
from the lateral part of the raised portion of the cord and 
form the caudo-lateral part of the arms. ‘These strands are 
the ascending fibres of the sensory trigeminus ; (2) two 
small bands running from the median part of the dorsal 
swelling of the cord along the median faces of the arms. 
These are the fasciculus communis of each side, and are 
visible on the dorsal surface from the caudal end of the 
medulla to the fork of the Y (fig. 1, f.c.). They are much 
thicker at the caudal end than at the cephalic; (3) the third 
division lies between the communis and the sensory trige- 
minus, and consists of the tuberculum acusticum, the 
“dorso-lateral strands’ of Goronowitsch and some other 
writers. After the arms of the Y have separated, the acustic 
bundles run along their inner border to the cephalic end of 
the medulla (fig. 1, ac.). Kntering the acusticum, ‘12 mm. 
caudad of the hind end of the cerebellum, is the acustico- 
lateral nerve acusticus J—in young forms, where the cere- 
bellum extends farther caudad, relatively, over the medulla, 
this nerve enters the medulla in front of the hind end of the 
