ANATOMY OF THE FLOOR OF THE FOURTH VENTRICLE. 
(The relations between the surface markings and the underlying structures.) 
BY 
GEORGE L. STREETER, M. D., 
Demonstrator, Anatomy of the Nervous System, Albany Medical College. 
From the Senekenbergisches anatomisches Institut, Frankfurt, a. M. 
WiTH 4 PLATES AND 2 TEXT FIGURES. 
In the following study I have undertaken to find out how much of 
surface anatomy can be seen in the floor of the fourth ventricle, and 
what relation this bears to the underlying structures. This has been 
done with the end in view that it might lead, not only to a more accu- 
rate knowledge concerning the anatomy of the nuclei and the tracts 
which le in the ventricular floor, but also might be of immediate prac- 
tical use to the pathologist in the cutting of material from this region 
to the best advantage, and in the identification of the extent and situa- 
tion of morbid processes. 
Naturally, this is not the first time that the task of determining the 
relations between the surface anatomy of the floor of the medulla and 
the underlying parts has been undertaken. As far back as 1840 Arnold 
and Stilling were working on the same problem, and later we have the 
remarkable work of Clarke. But from that time on, following the in- 
troduction of new staining methods, the attention of anatomists has 
been given almost entirely to the study of the finer histology of sections 
without regard to surface relations. On going back through the liter- 
ature, one finds everywhere the same descriptions of the floor of the 
ventricle, and all based on the researches of the previous investigators. 
In 1896, however, Retzius published his admirable work showing how 
much more complete the gross description of the brain could be made 
by a careful study, such as modern anatomv demands. On reading 
his description of the floor of the fourth ventricle, one first realizes 
how many structures had been overlooked which can be seen in the 
ventricular floor, and how far the descriptions commonly given in text- 
books vary from the conditions actually present. Retzius, however, does 
not include in his description of the brain the finer internal anatomy, 
and so makes no attempt to explain the significance of the various 
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