The chorio-allantoic membranes of White Leghorn chick embryos at 10 to 12 days after laying were fixed in Palade's buffered osmium tetroxide or in Luft's potassium permanganate.
After fixation in these two ways the general appearance is similar, but there are differences in certain tissue elements. Cell membranes are well preserved after fixation in KMnCv Certain lipid inclusions in the cytoplasm of the cells of the allantoic layer are well seen after fixation by OsO4, but not after KMnO4; in their places empty vacuoles are seen.
Details of the structure of the red blood-corpuscles are more clearly seen after fixation in KMnO4.
Otoconia are microscopic geometric structures that cover the sensory epithelia of the utricle and saccule (gravitational receptors) of mammals, and the lagena macula of birds. The importance of otoconia for maintanance of the body balance is evidenced by the abnormal behavior of species with genetic defects of otolith. Although a few reports have dealt with otoconia formation, some basic questions remain unanswered. The chick embryo is desirable for studying otoconial formation because its inner ear structures are easily accessible, and its gestational period is short (21 days of incubation).The results described here are part of an intensive study intended to examine the morphogenesis of the otoconia in the chick embryo (Gallus- domesticus) inner ear. We used chick embryos from the 4th day of incubation until hatching, and examined the specimens with light (LM) and transmission electron microscopy (TEM). The embryos were decapitated, and fixed by immersion with 3% cold glutaraldehyde. The ears and their parts were dissected out under the microscope; no decalcification was used. For LM, the ears were embedded in JB-4 plastic, cut serially at 5 micra and stained with 0.2% toluidine blue and 0.1% basic fuchsin in 25% alcohol.
The present communication concerns the influence in the chick (Gallus domesticus) of the growing eyes on various structures which form the wall of the orbits, or which lie in their vicinity. Features of the development of the trabeculae cranii, the fronto-nasal process, the nasal capsules, the maxillary ‘process’, the otic capsule, and the cephalic flexure will be described as well as certain growth relationships of the upper and lower jaws.
The methods employed include (1) removal of one or both primary optic vesicles, (2) the grafting of an additional primary vesicle into the head mesenchyme so that two eyes develop in one orbit, and (3) the isolation in the coelom of various head components.
The importance of the trabeculae to our present study stems from the fact that they contribute to the boundaries of the orbits on their medial sides.
The epidermis of the chick embryo has been widely used for in vitro studies of many developmental problems (Matoltsy, 1960; Billingham & Silvers, 1963). The present attempt to determine the proliferation rate of chick embryonic epidermal cells was expected to provide a base for experimental studies, but a preliminary mitotic count revealed that the number of mitoses varied greatly in different areas. This suggested accumulation of mitoses in some restricted parts of the epidermis, and so a mapping experiment was carried out to determine the distribution of mitoses in this material. The characteristic mitotic pattern which was discovered is described and discussed.
About 300 White Leghorn embryos were used: 20 for study of the gross anatomy of scales, 200 for Colcemid treatment and 80 for [3H] thymidine treatment.
Observations on the Composition of the Subcutaneous Fat of the White Leghorn Chick Embryo