3) 
344 The “ Papille of Retzius” and the Cortex of Embryos 
of His, which he pictures in Figs. 75, 77, 98 and 99. It shows that it 
is possible by different methods of maceration to produce experimentally 
typical cortical papillz in brains where they are not normally present. 
CONCLUSION. 
The comparison of Figs..1 and 2, one with, and one without cortical 
papillw, suggests the probability of the abnormal character of the papille. 
One could still perhaps raise the objection that they may be normal, but 
very transitory, and that the two sections do not quite represent the same 
stage of development, so that in Fig. 2 the papillae have either already 
disappeared or have not yet developed. This objection, however, can no 
longer be considered in face of the fact that in pigs, where one is able 
to secure specimens in exactly the same stage of development, it is possible, 
as has been shown above, to produce the papille by means of maceration, 
and furthermore to control their size and character by varying the degree 
and method of maceration. 
From the experience derived from the above experiments, as regards 
conditions which predispose to artificial fissures of the cortex and deformi- 
ties of its constituent cell layers, it becomes evident that embryo brains, 
which are intended for general morphological study, should, up until the 
time of completion of the principal fissures, be hardened in situ without 
disturbing the brain coverings. If the brain of a human embryo fresh 
from the uterus is uncovered or completely removed, and then immediately 
immersed in formalin or other fixative, it will not necessarily be free from 
abnormal fissures, etc. The framework of the brain wall up to that time 
is by no means firm, and it must be also remembered that it may already 
have been softened by maceration in the uterus. Thus in such a ease, 
and much more so in the embryos that do not reach the hardening fluid so 
promptly, it is essential that the brain coverings should be left intact, that 
they may serve as a support to the brain during the process of fixation. 
Imperfect penetration of the preserving fluid is to be obviated by injecting 
it through the blood-vascular system. 
LITERATURE. 
His, W., oo.—Développement de la substance grise de l’écorce cérébrale. XIIle 
Congrés international de Médecine. Paris, 1900. 
o4.—Die Entwickelung des menschlichen Gehirns. Leipzig, 1904. 
HOocHSTETTER, F., 98.—Beitrage zur Entwickelungsgeschichte des Gehirns. 
Bibliotheca Medica, A. Heft 2., Stuttgart, 1898. 
MatL, F. P., 03.—On the transitory or artificial fissures of the human cere- 
brum. Amer. Jour. of Anat., Vol. II. 
RETZIUS, G., 95—Das Menschenhirn. Stockholm, 1895. 
