The thyroid gland of sexually immature dromedary camels was studied using both light and electron microscopy. The thyroid gland contained follicles of different sizes in both summer and winter. However, most of the follicles were large in summer and small in winter. The large follicles were lined by very low cuboidal or semi-squamous follicular cells whereas the small ones were lined by high cuboidal or low columnar follicular cells. Electron microscopy showed that the very low cuboidal follicular cells were poor in organelles and were considered hypoactive. High cuboidal follicular cells on the other hand, were rich in organelles that included mitochondria, cisternae of rough endoplasmic reticulum, secretory vesicles, colloid droplets, heterosomes and autophagic vacuoles; they were considered to be very active. The possible role played by these organelles is synthesis of thyroglobulin and liberation of tri- and tetraiodothyronine is discussed. A few degenerate follicular cells were infrequently encountered in the camel thyroid. Parafollicular (C) cells were not seen in this study either with light or electron microscopy.

Taha A. A. M., A. B. Abdalla: Light and Electron Microscopy of the Sweat Glands of the Dromedary C_I. Acta vet. Bmo, 49,1980: 31-35. A light and electron microscopic study was made on the sweat glands of the dromedary camel using 42 experimental animals. The glands were present in all the regions studied except the lips, extemal nares and perianal region. The secretory tubule was made up of columnar, cuboidal or, sometimes, fiat epithelium. No glycogen was detected in the gland. Cell organelles were few but mitochondria were numerous. There was no evidence that the gland was of the classical apocrine type. Body regions, secretory cells, organelles.Only few studies have as yet been made on the structure of the sweat glands of the dromedary camel. Dowling and Nay (1962) stated that the secretory cells of the sweat glands of the camel were cuboidal to columnar. Lea and Schmidt-Nielsen (1962) studied 23 regions of the skin of two Saharan camels. Their findings indicated that the sweat glands were present in all the skin areas studied with the exception of the lips, extemal nares and the perianal region. The secretory cells were of the low columnar type.On the other hand numerous studies have been made on the structure of the sweat glands in other mammals. With the light microscope the sweat glands have been studied in the horse (Takagi and Tagawa 1959), dog (Takahara and Kato 1965), cattle (Hafez, Badreldin and Shafei J955; Goldsberry and Calhoun 1959;Nay 1959;Jenkinson and Nay 1975), water buffalo (Prusty 197,1, 1973;Jenkinson and Nay 1975) and goat and sheep Genkinson and Nay 1975). The ultrastructure of the sweat glands has been studied in cattle (prasad 1973). It is now generally held that the sweat glands of mammals are of the classical apocrine type.The present investigation is intended to throw more light on the histology of the sweat glands of the camel. Moreover, it is clear that there has so far been no ultrastructural study of the glands of this animal. Materials and MethodsMaterial for this study was collected from Tambul camel market, about 120 kilometres to the South of Khartoum. Forty-two adult camels were used, of which 15 were males and 27 females.For the study of the distribution and histology of the glands, pieces of the skin were taken from 33 regions of the body (Table 1) immediately after the animal was killed. The tissue was fixed in 10 % formol saline, Bouin's or Lavdowsky's fixative, dehydrated in alcohol, cleared in Cedarwood oil and embedded in paraffin.. Sections, 8-:10 pm thick, were stained with haematoxylin and eosin. Selected sections (Table 1) were stained with the periodic acid-Schiff reagent (P. A. S.) for glycogen, with or without prior treatment with malt diastase.For electron microscopy pieces of the skin were taken from the left lateral aspect of the neck of two adult females. The tissue was fixed by immersion in 3 % glutaraldehyde in 0.2 M cacodylate buffer (pH 7.4) with sucrose. After 24 hours the tissue was thoroughly washed in the buffer, post-fixed for two hours...

The poll glands of the camel are tubuloalveolar glands. They consist of lobules separated by interlobular connective tissue. Adrenergic axons and blood vessels including fenestrated capillaries are present in the intralobular connective tissue in close proximity to the secretory cells. The prominent features of the secretory cell cytoplasm are many mitochondria, smooth endoplasmic reticulum, and many vesicles in various secretory stages. It is concluded that the secretory cells have apocrine as well as merocrine modes of secretion. The glands may have the ability to uptake hormones and concentrate them. Additional work is needed before considering these glands as steroid-secreting glands.

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