The present study was conducting aiming to throw the light on the retinal structure on the level of both light and electron microscope. Eyeballs of 35 adult clinically healthy goats of both sexes were collected from Beni-Suef abattoir. The eyeballs were clinically examined before they were dissected and fixed in 10% buffed neutral formalin and in Bouin's solution for 24 hours. The specimens were then processed for light and transmission electron microscope. The retina (pars optica retinae) of the goats extends rostrally to cover the ciliary body as pars ciliaris retinae and the iris as the pars iridis retinae. Pars optica retinae and pars iridis retinae form the light non sensitive parts of the retina, while the sensitive part except at the transition zone; the ora serrata and the optic disc, appeared to be formed of ten layers, named from outward to inward as, retinal pigmented epithelium, rods and cones layer (photoreceptor cell layer), external limiting membrane, outer nuclear layer (cell bodies and nuclei of the photoreceptor cells), outer plexiform layer, inner nuclear layer (contained the horizontal, bipolar, Muller and amacrine cells), inner plexiform layer, ganglionic cell layer, nerve fiber cell layer (unmyelinated nerve fibers) and internal limiting membrane.

The sinu-atrial node (SAN) is one of the impulse conducting system of the camel heart. Anatomically, it lies beneath the epicardium, at the cranial end of the terminal sulcus, near the junction between the superior vena cava to the lateral wall of the right atrium and the right auricle. Histologically, SAN is located in the subepicardial layer of the terminal crest and can be identified as a mass of specialized and modified cardiac myocytes. Moreover, it appeared elongated in shape and bent oblong. SAN appears strongly similar to the general structure of the glands where, it is formed of two parts; the stroma and the parenchyma. The stroma is consisted of a fibrous connective tissue capsule that is completely investing the SAN from all sides. From the capsule, thin connective tissue septa or trabeculae are extending to inside the node, dividing the later into lobes. These lobes form the SAN head or the SAN body. From this body, the SAN arms processes take their way out. These arms are considered the internodal and interatrial pathways to the different sites in the right and left atria. So, the SAN head with arms giving the octopus like-appearance for the node. The parenchyma is consisted of three different types of specialized and modified cardiac myocytes; the perinuclear clear zone cells ("P" cells), the transitional cells ("T" cells) and the atrial Purkinje like cells or Purkinje like conducting cells.

Samples from medial retropharyngeal, superficial cervical and deep femoral lymph nodes of four camels were fixed in neutral buffered formalin and prepared for light and electron microscopic examination. The camel lymph nodes were formed of stroma and parenchyma. A dense collagenous capsule and trabeculae beside fine reticular framework represented the stroma. The parenchyma was formed of follicular and non-follicular forms of lymphoreticular tissue. The lymphoid follicles were mainly secondary in nature formed of germinal center and outer corona. Afferent and efferent lymph vessels were noticed at the same area of the capsule. Capsular, subcapsular, trabecular, peritrabecular and parenchymal lymph sinuses were noticed in camel lymph nodes.

The present study aimed to ellucidate the prenatal developmental stages of the submandibular salivary gland of the New-Zealand rabbits. To conduct that, twenty New-Zealand rabbit fetuses ranged from 11 to 30 days-old were used. The head region of fetuses and gland specimens were fixed, processed and stained with histological stains to be examined by light microscope. The submandibular primordia was firstly seen at the 12 th day of the prenatal life as bilateral invaginated epithelial buds from the linguo-gingival groove. At 15 days-old , such buds continued deep down growth forming cord-like structure ended by compact bulges that forming the future primitive acini. At 17 days, such cords were branched off forming the future primary ducts. Canalization of the ducts appeared at 18 days. At 22 days, the primitive capsule initiated around the gland and the lobulation was recognized. At 25 days, the capsule became well developed, the duct system was completed and the parenchyma occupied by serous adenomeres surrounded by myoepithelial cells. At the full term, the submandibular gland became fully developed and became typically compound tubulo-acinar nature, the parenchyma showed seromucoidadenomeres. Strong positive PAS reaction was noticed in the striated ducts, while the cytoplasm of the acinar cells reacted weakly.

The development of thyroid glands of New-Zeland rabbits was studied in 28 fetuses (10-30 days) and 28 rabbits (3 days-5 years). The thyroid premordia appeared at the 12 th day of gestation as 2 masses of cords and clumps of cells. The gland assumed the bilobed form with a narrow isthmus in between at the 18 th day. Small primitive follicles with narrow empty lumina appeared in 14-day-old fetuses. True follicles were recorded in 20-22 days old fetuses while colloid was seen in the lumina of the central follicles at the 24 th day. Light (C-or Parafollicular) cells were seen for the first time at the 12 th day. With development of the follicles, C-cells appeared between the follicular cells and some of them come in contact with colloid. The ultimobranchial body (UBB) was observed in 20 days old fetuses close to the thyroid anlage and entered into its tissue at the 22 nd day. Later on, it gave thyroid-like follicles or ultimobranchial cysts. With the electron microscope (EM) follicular cells of earlydeveloping fetuses were not yet differentiated. They contained few ill-developed rough endoplasmic reticulum (rER) and mitochondria. The organelles became well developed and the cells started to secrete colloid in full term fetuses. The maximum rate of secretory activity was achieved in the glands of adult rabbits. Changes in the thyroid glands during the postnatal life up to 5 years of age (age of senility) were followed up and described.