The ‘anatotopography of cranial thoracic inlets, the carotid body and associated structures in the caudal pole of the thyroid gland are described. The source from which the various groups of fowls (n = 65) were obtained as well as the varied localisation of the carotid body are indicated. In this investigation, the carotid body was found to be situated mostly (49 cases) either on or in the immediate vicinity of blood vessels (carotid and inferior thyroid artery) and only in 14 cases in close association with the parathyroids.

The histotopography of the silvery-white glistening carotid body and the branchial derivates in the cranial thoracic inlets as well as the histocytology of the particular organ were revealed by various microtechniques. Three types of randomly distributed epithelioid cells, many capillaries, and small and large sinuses are observable. Myelinated fibres are sparsely distributed. 25 clinically healthy white leghorn males were used for this investigation.

Sterba’s technique to detect neurosecretory substances was applied to carotid body tissue, surrounding branchial derivatives, ganglion nodosum and the carotid arterial wall. Mainly a yellowish-green, a yellowish-red and a bright yellow fluorescence was observed as well as greenish-yellow fibres with varicosities and terminal knobs. The metachromatic reaction of the technique was briefly discussed.

10 clinically healthy white leghorn males were utilised for this investigation. Apart from toluidine blue-pyronin-stained Araldite sections, uranyl acetate and lead monoxide staining revealed three types of epithelioid cells. Nuclear and cytoplasmic contents, especially three types of granules, conveniently designated as q, r and p granules, are described in detail and tabulated. Technical difficulties in obtaining carotid body tissue as well as clear-stained sections for ultrastructural studies are mentioned.

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