George L. Streeter 341 
of that layer, but it was nothing that approched the fungiform arrange- 
ment seen in the Retzius papille. As can be seen in normal specimens 
at this time, the pyramidal layer is split by a line of scanty nuclei into a 
Fic. 3. Section from a well-preserved brain of a pig embryo. 11.5 cm. 
long. This section shows that normally, in the pig brain of this age, the 
pyramidal zone presents a uniformly smooth outer surface. This brain, while 
still warm, was preserved in a chrome-acetic mixture. 
Fie. 4. Section from a macerated brain of a pig embryo, 11.5 cm. long. 
The brain was kept in normal salt solution 48 hours and then preserved 
in formalin followed by Miiller’s solution. The section shows distinct fungi- 
form clumping of the cortical cells and characteristic Retzius papille. The 
same specimen is shown under higher power in Fig. 6. 
more superficial thicker subdivision, the pyramidal cells proper, and a 
deeper subdivision which is to form the layer of polygonal cells. This 
stratification was preserved in the experimental material. Another feature 
of importance was the absence of the so-called transitory fissures. 
