The structure, distribution and dimensions of skin strata and sweat glands have been investigated in Egyptian buffaloes and cattle. Samples from sixteen body regions were taken from three adult bulls of both species. Identical studies were also made on one buffalo calf and two buffalo embryos. Serial vertical and horizontal sections were cut from each body region using the ‘terpineol paraffin wax’ method. The following results were obtained.
1. Buffalo skin is characterized by dermal papillae enclosing papillomatous epidermis. The fibrous structure of the dermis is similar in both species. In buffaloes, the average thickness of skin, main epidermis, papillomatous epidermis, and cornium is 6·5 mm., 50, 115, and 11μ respectively. The epidermis coefficient is 12 for the main epidermis and 18 for the papillomatous epidermis. In cattle, the average thickness of skin, epidermis and cornium layer is 4·3 mm., 51 and 5 μ respectively, while the epidermis coefficient is 8.
2. The average number of hair follicles per sq.cm. of skin is 394 in the buffalo and 2633 in cattle. Each hair follicle is accompanied by two large lobulated sebaceous glands in the buffalo, and one small bilobed gland in cattle.
3. There is no species difference in the histology of the sweat glands. Each hair follicle is accompanied by one sweat gland in both species. In the buffalo, the body of the sweat gland is oval and convoluted, while the duct is twisted at its attachment to the body. In cattle, the body of the gland is elongated while the duct is straight. The number of sweat glands per sq.cm. of skin is 394 in the buffalo and 2633 in cattle. The dimensions of the sweat glands are larger in buffaloes than in cattle. The length, circumference and sweating surface of the gland is 0·58, 0·47, and 0·276 sq.mm. in the buffalo, and 0·47, 0·26, and 0·124 sq.mm. in cattle respectively. The glandular surface of sweat glands per sq.cm. of skin is 1·07 sq.cm. in the buffalo and 3·08 sq.cm. in cattle.
4. The type of sweat gland secretion is apocrine in both species. In the buffalo, successive stages of apocrine secretion are observed, and the merocrinelike form is rare. In cattle, the merocrine-like form prevails and the other stages are very rare. The theory (Findlay & Yang, 1950) of intraluminal transformation, of secretory products from coarse granularity to fluid homogeneity is supported. The effect of locality on the type of sweating activity is stressed.
5. There are species differences in the distribution of blood vessels and capillaries. In the subepidermal level, the arterial branches are more frequent and superficial in buffaloes than in cattle. Capillaries are found in the dermal papillae of buffalo skin. The capillary loops encircling the hair follicle are more frequent in cattle than in buffaloes. The blood capillaries supplying the sebaceous glands are more numerous in the buffalo than in cattle. The blood supply of sweat glands is poor in both species.
6. There are age differences in the skin histology. The number of hair follicles per sq.cm. of skin in a 5-months-old embryo, calf at birth, and adult buffaloes is 10560, 1248 and 400 respectively. There are no skin glands in the 1-month and 5-months-old embryos. The sweat gland in the calf is small in size and similar in structure to that of the adult. Calves have fewer sweat glands than adults.
7. The body conformation and the degree of pigmentation are affected by species, breed and locality.
8. The secreting activity of the sweat glands may be affected by the locality.
9. It seems that there are species differences in the mechanism of heat convection and radiation, insensible perspiration and sensible perspiration, due to histological differences.