The cutaneous glands are originally merely solid cone-shaped growths of the epidermis, which sink into the underlying corium (Figure 2.286 1). Afterwards a canal (2, 3) is formed inside them, either by the softening and dissolution of the central cells or by the secretion of fluid internally. Some of the glands, such as the sudoriferous, do not ramify (Figure 2.284 efg). These glands, which secrete the perspiration, are very long, and have a spiral coil at the end, but they never ramify; so also the wax-glands of the ears. Most of the other cutaneous glands give out buds and ramify; thus, for instance, the lachrymal glands of the upper eye-lid that secrete tears (Figure 2.286), and the sebaceous glands which secrete the fat in the skin and generally open into the hair-follicles. Sudoriferous and sebaceous glands are found only in mammals. But we find lachrymal glands in all the three classes of Amniotes--reptiles, birds, and mammals. They are wanting in the lower aquatic vertebrates. (FIGURE 2.286. Rudimentary lachrymal glands from a human embryo of four months. (From Kolliker.) 1 earliest structure, in the shape of a simple solid cone, 2 and 3 more advanced structures, ramifying and hollowing out. a solid buds, e cellular coat of the hollow buds, f structure of the fibrous envelope, which afterwards forms the corium about the glands.) The mammary glands (Figures 2.287 and 2.288) are very remarkable; they are found in all mammals, and in these alone. They secrete the milk for the feeding of the new-born mammal. In spite of their unusual size these structures are nothing more than large sebaceous glands in the skin. The milk is formed by the liquefaction of the fatty milk-cells inside the branching mammary-gland tubes (Figure 2.287 c), in the same way as the skin-grease or hair-fat, by the solution of fatty cells inside the sebaceous glands. The outlets of the mammary glands enlarge and form sac-like mammary ducts (b); these narrow again (a), and open in the teats or nipples of the breast by sixteen to twenty-four fine apertures. The first structure of this large and elaborate gland is a very simple cone in the epidermis, which penetrates into the corium and ramifies. In the new-born infant it consists of twelve to eighteen radiating lobes (Figure 2.288). These gradually ramify, their ducts become hollow and larger, and rich masses of fat accumulate between the lobes. Thus is formed the prominent female breast (mamma), on the top of which rises the teat or nipple (mammilla). The latter is only developed later on, when the mammary gland is fully-formed; and this ontogenetic phenomenon is extremely interesting, because the earlier mammals (the stem-forms of the whole class) have no teats. In them the milk comes out through a flat portion of the ventral skin that is pierced like a sieve, as we still find in the lowest living mammals, the oviparous Monotremes of Australia. The young animal licks the milk from the mother instead of sucking it.