الفهرس 
Arabic summary
PLATE IOnly 14 pages are availabe for public view
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Abstract
The present work was suggested to study the structure, differentiation and histochemistry of the olfactory system (olfactory nasal epithelium, olfactory bulb and olfactory nerve) during the developmental stages of chick embryo; Gallus domesticus.
Different stages were selected for that purpose starting from 33-hour stage (stage A) to the adult chick (stage K).
After the application of a number of histological and histochemical techniques, it was found that:
1-In the 48-hour stage (stage B), the two olfactory placodes began to invaginate forming the nasal sacs.
The olfactory region of the nasal sac started to differentiate into the olfactory nasal epithelium which at the 7-day stage (stage F) was composed of the olfactory cells, the columnar supporting and basal supporting cells.
Bowman’s glands appeared only in the newly hatched chick (stage J).
2-Axons of the olfactory cells in the olfactory nasal epithelium developed towards the wall of the telencephalon at the 4-day stage (stage D).
Some ectodermal cells migrated with the nerve fibers and was suggested to be the precursors of the Schwann cells.
The mesenchymal tissue also participated in the formation of the epineurium, perineurium and endoneurium of the olfactory nerve.
3-In very early embryonic stages (48-hr.& 72-hr.-stages B & C respectively), the anterior wall of the telencephalon which was formed of three layers (ependymal, mantle and marginal layers) started to differentiate into the various nervous elements of the olfactory bulb as the olfactory nerve reached the telencephalon.
4-The olfactory bulb, at the 7-8 day stage (stages F & G), was in the form of a narrow cavity surrounded by a lamellated wall.
In the latter, eight layers could be described; fibrous, glomerular, outer granular, outer plexiform, mitral-cell, inner plexiform, inner granular and ependymal layers.
5-Carbohydrate contents of the olfactory system in general were low in early embryonic stages then increased gradually by age.
6-Proteins were high in early stages, decreased in the advanced embryonic stages then increased once again in the post-hatched chick.
Protein was found mainly in the cytoplasm and nucleoli of nerve cells.
7-RNA was usually associated with proteins and its quantities varied in the same manner like proteins.
8-DNA was present only in the nuclei.
It was rich in dividing and differentiating cells but became weakly stained in the adult since it became highly dispersed in the form of fine chromatin granules.
It was concluded that the olfactory system of the chick was similar in its structure, steps of differentiation and to a certain extent in its histochemical characteristics to other vertebrates in some respects and differed in others.