THE DEVELOPMENT OF THE PARAPHYSIS IN THE 
COMMON FOWL. 
BY 
FRANKLIN DEXTER, M. D. 
Associate Professor of Anatomy, The Anatomical Laboratory, Harvard Medical School. 
With 9 TExT FIGURES. 
The moment that one begins to examine the literature of this sub- 
ject he cannot fail to be impressed with the difficulties which present 
themselves. The forebrain has been a favorite subject for study, con- 
sequently a great deal has been written on it, and so it is impossible to 
feel certain that all pertaining to it has been read. It has been con- 
sidered from many points of view, by means of different methods, and 
has received many names, either when considered as a whole, or in its 
subdivisions. It does not seem to me to be necessary to mention each 
individual paper which I have read, so propose to include only those 
in my list of literature which have an actual bearing upon this special 
subject. 
There is a difference of opinion in regard to the best subdivision of 
the forebrain, but all who have described it, as far as I know, take the 
velum transversum as its primary subdivider into an anterior division 
or prosencephalon, and a posterior division or diencephalon. The 
nomenclature lately proposed by Minot (9) although a trifle longer 
than that adopted by some writers, has the advantage of being more 
specific, and consequently I shall follow it, with the exception of the 
first subdivision. He subdivides the median line of the diencephalic 
roof into six divisions. First, the region of the post commissure. As 
he later points out in his paper, and I thoroughly agree with him, that 
this commissure is probably developed from the midbrain, and there- 
fore should properly be considered as belonging to that region. Since 
this is probably the case, I see no reason for describing it as a portion 
of the diencephalic roof. 
We will therefore omit this subdivision, and will consider the pos- 
terior commissure as a part of the midbrain, and will subdivide the 
median line of the diencephalic roof into five regions: 
