Talk:Paper - A case of accidental impregnation of cells in the brain of a human embryo of four months (1912)

A Case Of Accidental Impregnation Of Cells In The Brain Of A Human Embryo Of Four Months

William A. Hilton

From Cornell University and the Institute of Anatomy, University of Minnesota

Four Figures

The heads of twin embryos of about four months were fixed in Zenker's (luid. They were afterwards kept in the same jar, containing about 82 per cent alcohol, for several years. The brains were removed and stained in toto with paracarmin. The first of these to be sectioned took the stain very well and showed no sign of precipitate. The second was sectioned soon after this and it was noticed that although the stain was equally as good as in the first specimen, there was a considerable amount of precipitate throughout the series. Some of this precipitated material seemed to be irregularly massed in various parts of the brain, but much of it was well organized giving Golgi-like pictures of blood vessels, cells and fibers. Most of the impregnated cells were near the brain cavities and located in the ependymal layer. Most of these cells were bipolar with long processes extending out towards the surfaces of the brain (figs. 1, 2 and 3). In the more central portions of the sections there were a few masses, appearing like multipolar cells with many fine fibers, which were also impregnated. One of these masses shown in figure 3, was evidently a neuroglia cell, but those sho'wm in figure 4 were probably true nerve cells.

The cells Avere for the most part well impregnated in special regions of the ependyma and chiefl}' confined to that layer in all parts of the brain. Almost no cells were found in the cerebrum or cerebellum, while the ependyma of the thalamus, optic lobes and medulla had great numbers of cells, chiefly of a bipolar form, with long fibers. Perhaps some of these cells were stages of neuroblasts, but many if not most of them were evidently spongioblasts and were found with their cell bodies showing at all levels of the ependyma (figs. 2 and 3). In some places as in figure 3, some of these cells show bej^ond the ependymal layer.

The impregnation was very perfect in many cases. The size of some cells and especially some fibers was evidently exaggerated, judging from the adjoining unimpregnated but carmine stained nuclei (fig. 1).

In some of the impregnated cells at the borders of the ventricles, part of the material was seen to project into the brain cavity (fig. 3). This may indicate the position if not the form of cilia.

The precipitate obtained in cells, fibers and blood vessels, may simply be the deposit so often seen after mercuric chloride fixation; however the specimen described seems to have this substance organized as one

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WILLIAM A. HILTON

Fig. 1 Camera lucida sketch of cells from the olfactory region of a four-month human embryo. The outline of the ependyma is shown with impregnated cells. The nuclei of unimpregnated cells are also shown. X 550. •

Fig. 2 Camera lucida sketch from a portion of the inner surface of the brain near the hippocampus. X 550.

Fig. 3 Camera lucida sketch of cells, fibers, ependymal nuclei and deeper nuclei from the thalamus. X 550.

Ffg. 4 Camera lucida drawing of several cells from the deeper parts of the medulla. X 80.

would expect to find it in material prepared by Golgi's bichromate and sublimate method.^ Like results are given by the Cox modification of this method when both salts are used at the same time.^

1 Un nuovo processo di tecnica microscopica. Rendic. R. Inst. Lombardo, tome 12, 1879.

"^ Impragnation des centralen Nervensystems mit Quecksilbersalzen. Arch. Mikr.Anat. Bd. 37, 1891.