THE MAMMALIA— MAN AND BEASTS. 



83 



The young arc at first nourished entirely by the Milk secreted from the MammaB 

 or breasts of their mother. Each mamma is a conglomerate gland, covered with a 

 tenacious cellular tissue ; it is formed of rounded grains, separated from each other 

 by fat, and surrounded by spongy and cellular tissues. In the midst of this gland, a 

 number of lactiferous canals cross each other, being serai-transparent, susceptible of 

 dilatation, and re-uniting in several leading branches towards the nipple. Besides this 

 general conformation, there are several thoracic, epigastric, or hypogastric arteries, 

 independently of numerous lymphatic vessels, which carry their ramifications through- 

 out these organs. They are also very numerously supplied with nerves, for their 

 sensibility is very great. The nipple, which is only covered by a mucous tissue, 

 with a very fine skin and epidermis, is delicately sensible to the slightest touch. 

 •'* Elle est formee d'un tissu vasculaire particulier qui jouit de la propriete d'entrer en 

 \me veritable erection analogue a celle de la verge et du clitoris ; car ces organes ont 

 beaucoup de syrapathie entre eus. Elle recoit de sang et devient rouge et tres-sen- 

 sible alors. Les conduits s'ouvreut et sont prets a faire jaillir le lait de meme que 

 le sperme est ejacule par les canaux excreteurs des vesicules seminales. En effet, 

 il y a une grande ressemblance entre Taction de la glande mammaire et celle des 

 organes de la generation. 



The mammse may be placed, according to the species, on the breast, the groin, 

 or the abdomen. Their number is often relative to that of the young. In the larger 

 species, which have only one or two young at each birth, there are usually but two 

 mammae, whether pectoral or ventral. With the species of medium size, there are 

 most commonly eight ; although some may have as many as fourteen. 



The Carnivorous animals most commonly have from six to ten placed longitudinally 

 under the abdomen ; the Opossums and Kangaroos have four to eight, fixed within 

 a fold of skin, or inguinal purse, within which the young lodge securely. The Elephant, 

 as also the Quadrumana, usually have two upon the breast, as in Man. The female 

 Hog has from ten to twelve, and the Ruminantia, whose milk seems to bo more sub- 

 stantial than that of any other domestic animals, have generally two to four mammse. 

 These numbers point out the maximum limit to the number of young, which each 

 female, when in a healthy state, is capable of nourishing without inconvenience. 

 Among the gregarious tribes of Mammalia, the young recognise their mother with 

 surprising accuracy by the sound of her voice, or by the smell, in the midst of the 

 most numerous flock. Those young possessed of the greatest vigour will, however, 

 take milk from several mothers, at the expense of the weakest, which are thus de- 

 prived of a portion of the food intended for them by Nature. Some unnatural 

 mothers drive their young away on first approaching their udder, without exhibiting 

 the slightest compassion for the unprotected state of their ofi'spring, which are thus 

 in general left to perish. 



With the greater number of Mammalia, the young take and leave the breast ac- 

 cording to their wants ; but it is difi"erent with the Marsupialia, the young of which 

 attach themselves so forcibly to the mamm^, that they would rather permit them- 

 selves to be decapitated than leave the nipple. They remain continually in this 

 position until their bodies become entirely covered with hair, and they possess strength 

 suflicient to gambol around their mother. Among most species of this singular class 

 of Mammalia, the skin of the abdomen forms a purse or pocket containing the mam- 

 mse, and to which cavity the young resort for refuge, even after the time when they 

 cease to derive their sustenance from their mother's milk alone. Only two species 

 of Mammalia, the Ornithorhynchus and Echidna, are without any apparent mamma; ; 

 but many interesting questions regarding their habits, and especially the cares which 

 they bestow upon their young, still remain unsolved. 



It has been said that the young Elephant sucks with its trunk. This, however, is 

 an error, as it makes use of its mouth, in nearly the same manner as other Mam- 

 malia- 



The time of suckling varies with the period of gestation, as well as with the time 

 necessary for the growth of the young. Thus it is prolonged as long as the ninth or 

 tenth month in Man, the Horse, and the greater part of the larger quadrupeds, while 

 it is very short with the Rodentia, which have in each year a considerable number 

 of births. With the Guinea-pig, which is the most fertile of known Mammalia, the 

 period of lactation terminates in about twelve or fifteen days. 



After having fed their young during the days immediately succeeding to the period 

 of birth, entirely with the milk of their mammae, the females of the Carnivorous 

 animals take themselves to the chase, and bring home to their young difi'erent kinds 

 of prey, so as gradually to accustom them to the use of a more solid food. At this 

 time they seem to lose their natural ferocity, and gambol with their young ; but on 

 being attacked, they are only thereby rendered the more formidable. After having 

 tried every possible means to place their family in a place of security, they fight with 

 the most determined obstinacy and courage. The particular history of each species 

 exhibits, in general, many interesting details relative to the care which the female 

 takes of her young, until tbey are sufficiently strong to provide for themselves. As 

 soon, however, as they have attained this period, the mothers are often seen suddenly 

 to change their feeling towards their progeny, and drive away, with the greatest 

 obstinacy, the same young ones which had so long been the continual objects of 

 their warmest attachment. This is particularly observable in all those species which 

 experience a rut at a particular period of the year, and also most remarkably amon^ 

 the larger Carnivorous animals, who would soon become pinched for want, if too 

 many were permitted to reside together in the same district. 



It is commonly during the interval which elapses between the termination of lacta- 

 tion and the commencement of puberty, that the first or milk teeth are replaced by 

 others. This only happens to those species which have simple teeth, fixed by true 

 roots. It begins with the incisors, and ends with the molars, while it often happens 

 that the latter are not changed until long after the age of puberty. The Hog never 

 loses Its first teeth, as they do not fall, but always continue growing. In certain 

 other quadrupeds, the teeth continue to grow during the whole course of their lives, 

 such as the incisors of the Rodentia, the compound molars of some animals of the 

 same order, and those of the Elephants. The same property is observed in the 

 teeth of the Kangaroos as well as in the Elephants, but with this difference, that the 

 molars are developed from the back, of each jaw forwards, and do not grow out of the 



gums as in most other ^Mammalia. There are, however, numerous variations in these 

 respects among the several genera and species, as well as in the forms, which the 

 teeth present, according to the respective ages of the animals. Those Mammalia 

 which change their teeth, and especially the Carnassiers, experience at this critical 

 period the most painful nervous affections, which often prove fatal. 



In general, the term of life among the Mammalia is in direct proportion to the 

 time which they severally take in arriving at their full growth, exclusive of the period 

 of gestation. Buffon calculated, from many observations, that they lived seven times 

 the period of growth ; but it is very often only six times this period. 



Among the most remarkable exceptions to the above rule, we find Man, with whom 

 the average duration of life is far less than that of other species, relative to his time 

 of growth. As he does not attain his full size until about the age of twenty years, 

 his hfe ought to average a duration of 120 to 140 years. Several individuals have 

 attained these ages, and some have even passed them ; but of those few who survive 

 the first years of infancy, by far the greater number do not pass beyond the ages of 

 seventy or eighty. This anomaly to the rule of Buffon is due to a multitude of 

 circumstances, which it would be premature to detail at present; such as the mode 

 of life, the abundance and excess of food, the want of temperance, and other results 

 of an imperfect and misdirected civilization. 



For the same reason, the relation which the period of growth bears to the whole 

 term of life, is not without many exceptions among the domestic animals. On the 

 one hand, they receive the influence of a superabundant nourishment, and on the other, 

 are more frequently preserved from those excesses to which this abundance might 

 have given rise. Hence, the duration of life is often prolonged among the domestic 

 animals beyond the term already specified. 



The growth of the Horse being commonly completed in about four or five years, 

 it lives twenty-five or even thirty-five, provided the natural term of its existence has 

 not been shortened, as happens too frequently by ill treatment of every kind, by 

 violent fatigues, as well as the want of attention and suitable nourishment. This ^ 

 animal presents, notwithstanding, several instances of remarkable longevity, and some 

 individuals have been known to attain the advanced ages of sixty and even seventy 

 yeai's. 



As the Ass takes nearly as long as the Horse in reaching its full growth, the 

 duration of its life ought to be nearly the same ; yet it often breaks down before that 

 period through injxuries or neglect, which it receives most undeservedly from all 

 quarters. It is observed that animals, naturally disposed to chastity, live longer 

 than those of different propensities. The Jlule and Bardeau are usually unable to 

 procreate, and accordingly they hve longer than either the Horse or Ass. Very fre- 

 quently Mules die at the age of forty, and one has been known to attain the age of 

 eighty years. 



The Bull takes about two or three years in growing, and the natural period of its 

 life terminates at fifteen to twenty years. The Buffalo approaches the former very 

 nearly in both of these respects ; yet it appears to take a little longer time in reach- 

 ing its full growth, and hence lives to a more advanced age. The Sheep has nearly 

 the same period of growth, and also a corresponding period of life. The Goat ap- 

 proaches to the same terms, both in respect to its growth, and the duration of its 

 existence ; yet the extreme attachment of these two last-mentioned species to sexual 

 propensities serves to abridge the ordinary period of their lives, in those few cases 

 where Man does not terminate their existence suddenly for his own advantage. 



The Hog being two years in attaining its full development, may reach the age of 

 fifteen or twenty years, if not fattened before the term of puberty, as is most commonly 

 done, though some old Boars have been known to pass far beyond the above-men- 

 tioned terms. 



We may thus perceive that the relation of the period of growth to the duration of 

 life does not remain constant among the domestic animals. It is, however, more 

 precise with the wild Mammalia. The Lion lives twenty-five years according to 

 Buffon, though several Lions of the Tower Menagerie of London hved in confine- 

 ment to the extraordinary ages of sixty-three and seventy years, on the authority of 

 Shaw. The Mococo (Lemur catta) lives at least twenty years, the Rabbit eight 

 or nine ; the Hare seven ; the Mouse only a short time. The Elephant, it is said, 

 lives for two hundred years; the Bear thirty; and the Wolf fifteen or twenty. 



Further, the Dog usually lives fourteen years, though the hves of some individuals 

 have been prolonged to twenty ; the Cat lives nine or ten years, and the Dromedary 

 forty or fifty. 



Nothing positive is known regarding the ages to which the Seals and the Cetacea 

 respectively attain ; it is, however, probable, from their near approximation to the 

 Fishes, in external characters, that they resemble them also in the average duration 

 of life ; in other words, they live to a very advanced age. This presumption is fur- 

 ther confirmed with the Seals, by the fact that they take a very long time in growing. 



GENERAL EEVIEW OF THE MAMMALIA CONTINUED, 



The Structure of Teeth^tkeir growth—the phenomena of successive dentition— 

 their varieties of form. 



The teeth among the Maramaha are always found upon the jaws or maxillary bones, 

 which is far from being the case with the lower classes of vertebrated animals— the Rep- 

 tiles and Fishes. Though useful auxiliaries of digestion, they are by no means essen- 

 tial to that function ; for some animals are wholly destitute of teeth, and in others, they 

 are far removed both from the mouth and the intestinal canal. Their existence is not 

 exclusively proper to the vertebrated animals, nor are they always confined in them to 

 the bonps of the mouth. 



The teeth of animals may be defined as bodies, generally hard or of a calcareous 

 appearance, produced by the secretion of special organs, fortifj'ing the anterior parts 

 of the alimentary canal, and by the assistance of which, the greater part of these ani- 

 mals seize, retain, or divide the food with which they are nourished, while some em- 

 ploy them further as weapons of offence and defence. The teeth of the Mamroaha, 



