THE MAMMALIA— MAN AND BEASTS. 



67 



being general, it is confined to a very small proportion of the Animal Kingdom. 

 If this superiority of size were characteristic of the sex, the loss of the reproductive 

 organs during early youth ought to prevent it. The effect is, however, precisely 

 the contrary, for castration, which brings the constitution of the male near to that 

 of the female, is highly favorable to the growth of the former ; these organs were 

 therefore rather an obstacle to their development. 



This disparity seems to arise from the fact, that the nutritive powers of the female 

 are, in the JMaramalia, expended upon their offspring. The Cow, whose weight is, 

 perhaps, not one half that of the Bull, lives in a continual state of gestation or lac- 

 tation ; and it is the same with the Ewe and She- Goat. Every Grazier is aware, 

 that the young females cease to grow as soon as they begin to produce ; and that 

 yielding milk is still more prejudicial to their growth than gestation. 



If we compare the Ruminantia and Herbivorous Cetacea with the Pachydermata, 

 we shall find, that the young of the former consume much more milk than the young 

 of the latter ; and, accordingly, it is in the two classes first mentioned that the pre- 

 dominance of the male over the female in size is most decidedly marked. Indeed, 

 the Pig is the only Pachydermata which is very proHfic, and it is precisely in this 

 Genus that the male more sensibly exceeds the female in dimensions. Of all the 

 Rodentia, the Rats are the most fertile ; and the predominance of the male Rat over 

 his female is more apparent than in any other of the Rodentia. 



Those Mammalia which hve upon Insects and Fruits, such as the Cheiroptera and 

 Insectivora, do not exhibit the same difference of magnitude between the sexes as the 

 proper Carnivora. The females of the former, from their situation, find an easy and 

 abundant prey either in the larvce of Insects which hatch around them, or in the 

 Fruits which fall and ripen near their retreats. The female of the latter is obliged, 

 on the other hand, to pursue an alert and nimble prey, which often eludes her 

 pursuit. Her yoxuig ones are not deficient in number, and she consequently loses a 

 large quantity of nutritive power. From these causes, the male, who is always at 

 large, and lives for himself alone, is wholly exempt ; and hence the female of the Bat, 

 the Hedgehog, and the Mole, is at least as large as the male, while the Lioness is 

 smaller than the Lion. 



Among the Marsupialia, where the females produce an embryo, or rudimentary 

 fcetus, which always travels about with its mother, and cannot keep her confined to 

 a spot remote from her food, we find that the female is at least as large as the male. 

 With the Edentata and Tardigrada, the female is usually larger than the male. It 

 is especially remarkable in the Ant-eaters, where the female, by the aid of her long 

 tongue, an organ usually more developed in the female than in the male, enables her 

 to catch the Ants, her prey, n-ith a superior nimblenoss and agility. 



Among the domestic animals, whenever it happens that the female is made to work 

 like the male, and that she is not compelled to submit to a continuous and depressing 

 lactation, she does not yield to him in size. The She- Ass is as large as the male; 

 the Mare as the Horse ; and the Dog is not larger than his female. In these cases, 

 Man provides equally for their wants and necessities. 



Some Naturalists have considered the Polecat (Mustela foina) to be a domesti- 

 cated variety of the Jlartin (Mustela 7nartes). In the former, the sexes are of an 

 equal size, while the male is greater than the female in the latter. With the com- 

 mon Hare (^Lcpus timidus) the male is not so bulky as the female; on the contrary, 

 with the Rabbit (i. cuniculus) the male is the larger of the two. This evidently 

 may be traced to the superior fecundity of the latter species. 



We may easily see how the dimensions of animals should depend so much on the 

 quantity and quahty of their food, since all substances do not contribute an equal 

 quantity of nutriment. Vegetable substances, which arc mucilaginous and herbaceous, 

 contribute much more powerfully towards the development of animals than those 

 which are fibrous and of an animal nature. These are more favorable than acid 

 substances ; and tlie latter again surpass those which are saccharine. Thus among 

 all the Mammalia it is the Herbivorous and proper Cetacea, the Pachydermata, and 

 the Ruminantia, which attain greater dimensions than tlic Carnaasiers, and these again 

 than the Quadrumana and Edentata. The same thing may also be traced among the 

 Birds, for the Waders (GrnZ/ff) and the Web-footed Birds (Palmipedes) become 

 larger than the Birds of Prey {Accipitres), the latter are in then- turn larger than 

 the Thrushes (Turdus)^ and these again than the Humming Birds (Trochilus). 



This advantage in respect to dimensions, to which a plentiful supply of food con- 

 tributes, is unfavorable to reproduction, and hence acts ultimately against the species ; 

 for the difficulties of procuring a sufficient supply of food are always greater in the 

 larger than in the smaller species. Large species are hence comparatively rare upon 

 the earth, except where human industry has ministered to the insufficiency of their 

 own resources. The smaller races of Goats and Sheep might maintain themselves 

 without assistance in our temperate climates, but it would not be possible to preserve 

 the larger races of these animals; and with still greater reason of the Horse, the 

 Cow, or the Ass. 



The superiority of the male over the female ought then to be more apparent in 

 the larger than in the smaller species. With our Oxen and Sheep the difference 

 is greater among the larger than among the smaller races. It is greater in the Rat 

 than in the Mouse. This inequaUty between the sexes would have been still greater 

 in the largest species, if the deficiency of nutrition sustained by the female did not 

 become progressively less according as there exists a progressive diminution of fe- 

 cundity. Among those domestic animals, whose females supply ns continually with 

 milk, the inequality becomes enormous in the largest species, because frequent milk- 

 ing is still more unfavorable to development than a very great fecundity. Good Cows 

 fatten during gestation, and become lean when milking commences, whatever may 

 be the quality or quantity of their food. 



The primitive cause of this inequahty of size between the sexes seems to show a 

 tendency to return to an equilibrium ; and we may thence infer that there formerly 

 existed a greater disparity between the males and females of the Pachydermata than 

 at present, when we find this disparity still existing among the Amphibia, which are 

 more productive than the Elephant, the Rhinoceros, and the Hippopotamus. 



When the capacity of reproduction is extmguished, species arrive at their end. 

 We may infer that it is chiefly to the feeble powers of reproduction among the Pachy- 



dermata that we find so many fossil species belonging to this order which have no 

 living analogues. Species, like individuals, decline and die, when they have attained 

 the limit of their dimensions. 



From what has been said, it may easily be inferred that in those orders of animals 

 where the male is usually monogamous, and shares with the female the care of her 

 progeny, he is not in general susceptible of that superior development beyond the 

 female, as where he is polygamous. 



We have now seen that when two or more species of Mammalia resemble each 

 other perfectly in their generic characters, their height is the same, or but shghtiy 

 different. Those famiUes, genera, or species, which inhabit the bosom of the ocean, or 

 pass a part of their hves in the water, arrive at a large size comparatively to the other 

 families, genera, and species of the same group; and the increment of their dimensions 

 is the greater, all other things being the same, in proportion as their organization 

 renders them more essentially aquatic. The genera with wings, or which live in 

 trees, on the contrary, never attain to any but very small dimensions. Those Mam- 

 malia which are purely terrestrial, may be arranged in series according to their di- 

 mensions, very large in the first, less in the second, and so on, that is, into herbivor- 

 ous, carnivorous, frugivorous, and insectivorous. In other words, there always exists 

 an exact co-relation between the volume of the animals and the volume or quantity 

 of organized beings which they are destined, by the formation of their digestive 

 organs, to consume. 



It has also been shown that there exists a constant relation between the height of 

 the Mammalia and the extent of the places where they live ; the largest species 

 inhabit the oceans, continents, or large islands; the smaller reside in rivers or small 

 islands. Even the Mammaha of a more extensive continent surpass in dimensions 

 their analogues of a less extensive continent, and the Mammalia of the Northern 

 Hemisphere are larger than the corresponding animals of the Southern. In general, 

 also, i&ough not always, the height of Mammalia resident in the mountains is inferior 

 to that of the analogous animals residing in the plains. 



The preceding observations are true without exception in reference to the Mam- 

 malia, but when appUed to lower classes of animated Nature, they gradually lose 

 their general correctness, and are finally lost when we arrive at the lowest classes of 

 all, in an infinity of exceptions. We, however, always find that when other circum- 

 stances remain the same, the variations of size observable in any one class are always 

 confined within narrower limits in proportion as that class is more natural. 



We have also seen that the size of the body depends upon the quantity of nutritive 

 particles which it is capable of retaining. The female would always attain a larger 

 size than the male, as she is endowed with a greater power of absorbing nutriment, 

 did she not experience the influence of certain counteracting causes which do not 

 act upon the male. She has to submit to a severe lactation, in many cases to a fre- 

 quent parturition, and is often compelled to undergo privations of food in her cares 

 for her offspring. As these causes do not affect the male, there hence arise inequalities 

 in their dimensions, or relations of volume, and these differences of size between the 

 sexes, when they exist, depend upon the intensity of these causes. It must, how- 

 ever, be admitted, that sometimes the relative sizes of the sexes seem to be inex- 

 plicdble by any of the causes just enumerated, and in these cases we must infer that 

 differences in the bulk of the sexes have been originally impressed upon the species at 

 the moment of their creation. 



GENERAL RETIEW OF THE MAMMALIA CONTINUED. 



Phenomena of Nutrition among the Mammalia — Manner of ohtaini7iff their Food. 



That Animals can only be nourished by substances which have once lived, in other 

 words, by other Animals or by Plants, we have already had occasion to explain. 

 Some persons have hastily concluded, from imperfect observations, that animals can 

 nourish their bodies with inert mineral substances. This opinion is, however, erro- 

 neous. That yellow earth which the famished Wolves have been seen to swallow in 

 their rage, serves but to deceive the intensity of their hunger. The MoUusca do not 

 devour the fragments of rocks or old wood which they destroy or perforate, nor do 

 Birds digest those hard mineral substances which are sometimes found broken or 

 pulverized in their gizzards. 



The food of the Mammalia is very various, since it takes in all other animals and 

 vegetables. There always exists a certain correspondence between the degree in 

 which the organs of an animal are complicated, and the nature of the food which it 

 consumes ; for it has been generally remarked, that the simplest beings always require 

 the simplest food. The Tiger feeds on a Uving prey, the Wolf upon carcasses, the 

 Otter upon fish, the Hog upon roots and animal food, the Myrmecophaga upon 

 ants, the Apes upon fruits, the Rodentia and Rummantia upon simple herbs, Man 

 and the Bear upon almost any thing. 



Thus we may remark among the Mammalia the greatest diversity in their tastes 

 for food. While in some the nutriment wholly belongs to the Animal Kingdom, in 

 others it is as entirely confined to the Vegetable. Others again, whose nourishment 

 is mixed, seem to avail themselves at once, or indifferently, of the produce of either 

 Kino-dom. These varieties are usually expressed by the terras sarcophagous or car- 

 nivorous, phytophagous or herbivorous, polyphagous or omnivorous. 



These first differences of animals in respect to their food, presuppose or draw 

 along with them certain other differences in respect to their organs. A carnivorous ani- 

 mal has more teeth than an herbivorous one ; these teeth are more unequal, more fitted 

 for tearing, and more trenchant like a saw. His jaws are more free, more powerful, 

 and moved by larger and more vigorous muscles ; his stomach is not so large, and its 

 sides are thinner ; his intestines are shorter, and proceed within a slimmer form 

 throut^h a less capacious abdomen. His limbs are also differently disposed than in 

 the herbivorous animals, as the voracious instincts require instruments at once fitted 

 for agihty and destruction. 



Many carnivorous animals will only devour a living prey, which leads them to 



