depth, reminding one of the pair of marsupia in Echidna, save that the milk escapes in front of, and not into, the pouches.

§ 418. In Carnivora.-In the Seal-tribe, including the Walrus, the number of teats does not exceed four. In the Otters (Enhydra, Lutra) only two teats have been observed, ventral in position. The Mustelida have from four to six ventral teats. Six is the common number in Urside, two being pectoral and four ventral. In Cercoleptes I found but two ventral teats. Procyon, Meles, Taxidia, Nasua, have six; Ailurus has eight teats. The palm-cats (Paradoxurus) and Ichneumons (Herpestes) have four ventral teats. They seem not to exceed that number in the Hyænas; but in the Civets two pectoral nipples are sometimes added to the four ventral ones. The felines have usually six nipples, four ventral, and two pectoral; but in the domestic cat eight have been seen. The Canida, wolf, dog, jackall, fox, have usually

eight teats. § 419. In Quadrumana.-In the Aye-aye (Chiromys) there is but one pair of nipples, situated about an inch and a half in advance of the vulva, and one inch apart: they are sub-elongate, obtuse, with about a dozen terminal lacteal pores. pair of inguinal nipples some Lemurida (Stenops, Tarsius, Microcebus, e.g.) add a pectoral pair; while in Otolicnus and some kinds of Maki (Lemur catta, e. g.)' two pairs of pectoral nipples have been found.

To such a

In platyrhine and catarhine Quadrumana the mammary glands and nipples are restricted, as a rule, to a single pair, and to the pectoral region. In the ordinary quadrupedal progression, the young, with its belly applied to that of the mother, clings back downward, by the fore and hind feet to her flanks, holding on by the mouth to the teat between her fore-legs. In the seated posture the mother ape holds her young to the nipple by the fore-limbs, in a very human fashion. The integument covering the mammary gland is not protruded by its enlargement in the form of a hemispheroid breast:' it is covered with hair, like the rest of the body, becomes conical and pendulous, with much elongation of the nipple, as the suckling period is prolonged. In an Orang-utan (Pithecus satyrus), I have observed an accessory nipple on the left side, below the normal one and of smaller size. From ten to twelve lacteal ducts open upon the apex of the normal nipple in the Orang. Around the base of the nipple open the orifices of sebaceous ducts. § 420. In Bimana the mammary glands, two in number, are

609

subdepressed circular bodies, thicker at the middle than at the circumference, which, with the connected sclerous, areolar, and adipose tissues, raise the pectoral integument, at puberty, in the form of two large hemispheres or breasts;' and, from a little below the centre or apex of each, projects the nipple.' The base of the 'breast' corresponds to the interval between the third and the sixth or seventh ribs. The gland is of a firm texture and pale reddish colour: the secerning follicles, when injected with mercury, are just visible to the naked eye. Magnified four times, they present the appearance shown in fig. 609. They are aggregated in clusters or glandules' of different sizes, suspended by the duct resulting from the union of those of the follicles. The short or stemducts open into a wide canal, and these, fig. 610, c, d, by successive unions, form dilated reservoirs of a conical form, ib. b, b, from the apices of which are continued the

610

Secerning follicles and ultimate lobules of Human Mammary gland, injected with mercury; magn. four times. CCLXXXIV".

From a Cooperian preparation of parts of the Human mammary gland, injected from six terininal ducts, a, a, and dried. CCLXXXIV".

'straight ducts,' a, a, of the nipple. The gland is enclosed in a sclerous capsule, fig. 611, a, a, firmest where it is attached to the derm, whence are continued processes into the substance of the

gland subdividing it, or defining its lobes; and which, from their connection with the tegument, are called suspensory' ligaments. Finer processes connect the opposite surface or base of the gland

From a Cooperian preparation of the sclerous framework and attachments of the Human mammary gland. A bristle is passed behind some of the straight or terminal lactiferous ducts. CCLXXXIV".

with the fascia of the pectoral muscle, b, b. The nipple in the virgin is a rounded cone and nearly smooth; at sixteen years it is slightly wrinkled; at seventeen it has small papillæ upon its surface; from twenty to forty years the papillæ are large;

612

from forty to fifty the nipple becomes wrinkled; from fifty to sixty the nipple is elongated; and in old age it usually has a warty appearance. When in use its extremity expands and shows the circularly disposed conspicuous pores of the lacteal ducts. The papillæ of the nipple, fig. 612, are directed toward its apex. The coloured portion of skin around the base of the nipple is the areola:' it expands and changes from a reddish colour to a dark brown, after impregnation. Around the base of the nipple are orifices of complex sebaceous glands. The skin of the areola is covered with papillæ, like those of the nipple, but of smaller size; they are disposed in circles, directed toward the nipple, so that

Sensitive papillæ of the Human nipple and areola; nat. size. CCLXXXIV".

they also are opposed to the papillæ of the lips of the child: being highly vascular and nervous, they yield, when so grasped, a sensation which is followed by erection of the nipple through a fitting arrangement of its vascular tissue. The homotypal gland, in the male, varies from four lines to two inches in diameter. ASTLEY COOPER succeeded

in demonstrating its conformable structure to the functional gland in the female: fig. 613 is taken from his preparation. Under special circumstances and stimuli

such gland may be developed

613

Secerning follicles and ducts of the male mammary gland, injected with quicksilver; nat. size. CCLXXXIV".

so as to afford sustenance to
the infant, of which more than one case has been recorded.

The chief varieties in the female mammary organs relate to prolonged periods of lactation, as in those inferior races in whom the dugs become so extended as to permit the nipple to be thrown over the shoulder to the child carried on the mother's back. CUVIER noted an unusual breadth of the mammary areola in the Hottentot Venus.' 1

Anomalies of supernumerary nipples and glands are rare.

2

On a retrospect of the comparative anatomy of the mammary organs we see that the modifications of these persistent tributaries to the growth of the young mammal serve as little to characterise groups as do the deciduous nutritive organs at the uterine period of life. A pair of pectoral mamme would associate together as heterogeneous an assemblage of species as does the diffused, or even the discoid, placenta. We may, however, discern in part, the uses of mammary modifications; whilst the teleological relations of a zonular, a cotyloid, or a cotyledonal afterbirth can, at best, be but very vaguely guessed at.

§ 421. Adipose substances.-These are common to all organisms, protozoa, plants, animals.3 In Mammalia they exist

1 CCLXXXV".

2 In the instance narrated in CCLXXXVI". the second nipple on each side was onesixth the size of the normal one, and situated near the anterior margin of the axilla. When gently pressed, a milky fluid flowed from several ducts opening upon its extremity. When milk was drawn from the normal breasts, a small quantity usually escaped from the superadded nipples, but their flatness prevented the mother suckling her children by them.

3 HUNTER, who sometimes clothed his far-reaching thoughts in paradoxical language, writes: Fat is no part of an animal: for first, it is not animal substance; secondly, an animal is the same without it as with it,-it is to be considered as an adventitious matter; and thirdly, it is found both in vegetables and minerals, and, therefore, is a

under conditions which vary in the degree of temperature required for congelation, as oil,' 'marrow,'lard,' 'spermaceti,' 'suet.' The most solid fats when subject to pressure afford some fluid oil, termed elaine,' and when the fluid fats are cooled to about 32° they deposit a concrete element called 'stearine : ' the temperatures of congelation indicate the varying proportions of elaine and stearine. Whether or not it be in relation to the degree of cold to which the hoofs of some ruminants are subject, in traversing the snows of arctic climes, the oil called neat's foot' owes its use in the arts to its maintaining its fluidity below the freezing point. Blubber-oil, which becomes lardy at 45° or 50° Fahr., and is fluid above 55°, most abounds in the thick subcutaneous tissue of the Cetacea. The fat of the hog-tribe, horse-tribe, most Lissencephala, Carnivora, Quadrumana, and Bimana, is in the state of lard.' It exists as suet and tallow in Ruminants. Spermaceti is peculiar to the Cachalot whales (Physeter, Euphysetes).

Some Rodents, the Hare, e. g., show little or no fat; but it occasionally accumulates in the tame Rabbit. In many Rodents it is limited to the abdominal cavity and its special peritoneal processes. In the Seal-tribe and Whale-tribe, on the contrary, there is no fat in the abdomen, or in the mesenteric or omental duplicatures of the lining membrane. The subcutaneous areolar tissue to which it is limited in these aquatic mammals has a coarser reticulate structure in the Seals, the Grampus, and Balancptera, than in the Porpoise, Sperm-whale, and Balana. In all Cetacea the containing tissue is finer upon the trunk, and coarser toward the tail. Fat is subcutaneous in the Hog and human subject, but is also present in the great serous cavities, intermuscular spaces and joints, in variable degrees.

Fat is to the adult what milk is to the young-a source of nourishment when no other is available. Certain Bovines of the tropics, where during the rainy season luxuriant grasses abound on plains parched up in the dry season, accumulate fat and other assimilable substances in a dorsal hump at the period of plenty, and absorb its contents during that of drought. The Camels, when their food abounds, store up similar superabundant nutritious matters in one (C. dromedarius) or two (C. bactrianus) larger humps: whereby they are able to endure unusual fasts by re

substance common to every class of matter.' xx. vol. iii. p. 209. The ternary compounds of carbon, hydrogen, and oxygen, discovered in the condition of petroleum and its allies, in mineral strata, are suspected, with good reason, to have originated in organic bodies.