r) 
340 The “ Papille of Retzius” and the Cortex of Embryos 
of the fixing fluid, the brain coverings were not removed until the speci- 
men was ready for embedding, and on the other hand, the maceration was 
produced either by keeping the specimens dry and exposed to the air long 
enough for them to macerate in their own fluids before they came into 
the fixative, or in other cases by putting the brains directly into normal 
salt solution for varying lengths of time. In human material His found 
the cortical papilla most marked in material hardened first in formalin 
and then immersed for several days in Miiller’s solution. So the same 
method of fixation was adopted in the experiments, the details of which 
are as follows: 
A. Maceration Followed by Imperfect Fixation. 
Al. Maceration in own fluids (11, 12, and 14 cm. pigs). 
Embryos left exposed to air, 18 hours. 
Embryos placed in formalin, 10%, 48 hours. 
Embryos placed in Miiller’s solution, 4 days. 
Washed, brought into alcohol, and then the brain coverings 
were removed and the brain imbedded and cut in paraffin. 
A2. Maceration in normal salt solution (12 em. pigs). 
Embryos placed in salt solution, 17 and 48 hours. 
Embryos placed in formalin, 10%, 48 hours. 
Embryos placed in Miiller’s solution, 4 days. 
Washed, brought into alcohol, and brain removed as above and 
the brain then sectioned in celloidin and paraffin. 
In these specimens, in which the brain coverings were left intact 
throughout the period of fixation, no cortical papillae were found. Em- 
bryos of different sizes were tried (A1) for the purpose of covering the 
whole period favorable to the formation of the papille. The poor preser- 
vation of the tissues manifested itself by a varying degree of fragmentation 
of the sections, particularly of the deeper parts. ‘The sections presented 
a shredded appearance which varied from minute forking clefts between 
small clumps of cells and between fiber bundles, up to large irregular 
cracks splitting the different layers of the brain wall. This condition was 
found both in material that was cut in paraffin and in that cut in celloidin, 
but it was more marked in specimens that had been macerated in salt 
solution 17 hours, and still more marked in those macerated 48 hours. 
Otherwise the general topography of the sections and the arrangement of 
the layers was fairly well preserved. 'The minute clefts between the cells 
of the pyramidal layer gave a slightly ragged appearance to the surface 
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