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| Location: |
World |
| Subject: |
Anatomy - Glands |
| Species: |
White Rhino |
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Ceratotherium simum preputial glands. Attention is here directed to the presence of certain hitherto undescribed and histologically peculiar glands which occur in the preputial skin of Ceratotherium and which constitute a most conspicuous external feature of the penile integument.
Preputial glands in Ceratotherium
In colour the skin of the penis of a 3 years old specimen of Ceratotherium simum is elephant grey with mauve undertones. Against this background certain white papillae stand out markedly. These papillae are encountered either singly, or in confluent clusters or short rows, upon the preputial skin adjacent to the glans penis, as also upon the glans itself and upon the outer surface of its lateral processes (fig. 1). Each papilla has the form of a low, flat-topped elevation, oval or circular in outline, and some 2 mm in maximum diameter, whose crateriform free surface presents centrallv the dark ostium of a largish crypt (Fig. 2). The naked eye appearance of such a papilla recalls (though on more diminutive scale) that of the smallest of the carpal glands present in Sus scrofa. Structurally each papilla is a cutaneous elevation related to a central crypt and to a more deeply situate ecerine sweat gland, associated, like the papillary skin itself, with a relatively enormous quantity of dense lymphoid tissue (Fig. 3). The papillary epidermis reveals a relatively thin stratum corneum, which is everywhere much infiltrated by lvmphoeytes and which lines the central crypt : dermal papillae are here shorter, more rounded and more widely spaced than in the surrounding preputial skin, where they are notably tall, slender and closely packed. The crypt is surrounded by an obtrusive mass of dense lymphoid tissue, which shows secondary nodules and extends towards, and into, the epidermis. Embedded in this lymphoid tissue, deep to the crypt, is a typically ecerine sweat gland, associated with myoepithelial cells, whose duct discharges into the crypt lumen. The dark-staining lymphoid tissue is strikingly obvious upon mere naked eye inspection of histological sections of the papillae. The presence of this lymphoid tissue must account for the formation of the papillae, since otherwise the ducts of the sweat glands could without hindrance open, through the crypts, flush with a non-elevated cutaneous surface.
This intimate association of lymphoid tissue with an ecerine sweat gland constitutes a most unusual histological finding, for which, seemingly, a parallel is not discernible elsewhere.
The ecerine sweat gland itself shows nothing histologically remarkable: all traces of mucin are absent from its secretion, which is obviously of a watery nature : but whether this secretion is odorous or otherwise cannot be determined on mere microscopicat evidence.
In Ceratotherium preputial skin apocrine sweat glands, sebaceous glands and hair follicles are present. In the skin elsewhere (neck, flanks, limbs) the apocrine gland is the only variety of sweat gland encountered, and is invariably attended by numerous, well developed myoepithelial cells. This finding harmonizes with the histological pattern of the body skin of non-Primate mammals generally. It might therefore be expected that the specialized pre- putial glands of Ceratotherium would prove to be of the apocrine variety and it is somewhat surprising to discover that the glands associated with the preputial papillae are unequivocally of ecerine type. The intimate association of active lymphoid tissue with these glands is also surprising and is not easy of explanation. The periglandular lymphoid tissue which characterizes the mucous glands of the alimentary and respiratory tracts is generally - and reasonably - credited with a protective role against bacterial invasion. It is however difficult to understand why the Ceratotherium preputial glands should be particularly vulnerable to infection and should thus require the protection afforded bv the presence of lymphoid tissue.
Discussion
The presence of apocrine sweat glands in the Ceratotherium preputial skin is not unexpected since this variety of sweat gland predominantes in the skin elsewhere ; it is commonly associated with the production of an odorous type of sweat, and the Ceratotherium penile region can be observed to exercise an olfactory attraction for the female of the species.
The presence of ecerine sweat glands in the Ceratotherium prepuce and glans is in agreement with the occurrence of such glands in the non-hairy skin regions (e. g. rhinarium, foot pads, genitalia) of other mammals. The intimate association of such ecerine glands with dense masses of active lymphoid tissue is, however, an altogether exceptional finding. It is common enough (e. g. in the lincrual, faucial and pharyngeal mucosa) to encounter mucus-secreting glands discharging into a central crypt and surrounded by abundant lymphoid tissue: it is, apparently, unknown elsewhere for an ecerine sweat gland to manifest any comparable association with lymphoid tissue. Histological methods alone attord no clue to the chemical nature of the secretion of these peculiarly specialized ecerine glands of the Ceratotherium penis, which are probably best interpreted as scent glands of sexual significance.
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The preputial glands of Ceratotherium
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