Observations on certain parts of the animal oeconomy. Inclusive of several papers from the Philosophical transactions, etc / by John Hunter ... With notes by Richard Owen.
- John Hunter
- Date:
- 1840
Licence: Public Domain Mark
Credit: Observations on certain parts of the animal oeconomy. Inclusive of several papers from the Philosophical transactions, etc / by John Hunter ... With notes by Richard Owen. Source: Wellcome Collection.
481/494 page 473
![position, and probably use, with the hog. The grinders would seem to be a mixture of hog and ruminant, the enamel on their ex- ternal and grinding surfaces rather formed into several cutting edges than points. There are six incisors in the upper jaw and only two in the lower, but these two are so placed as to oppose those of the upper; five grinders in each side of each jaw, the most anterior of which is small.* The proportions of some of the parts of this animal bear no analogy to what is common in most others. The disproportions in the length between the fore legs and the hind are very considerable, also in their strength, yet perhaps not more than in the jerboa. This disproportion between the fore legs and the hind is princi- pally in the more adult; for in the very young, about the size of a half-grown rat, they are pretty well proportioned ; which shows that at the early period of life they do not use progressive motion.t The proportions of the different parts of which the hind legs are composed are very different. The thigh of the kangaroo is ex- tremely short, and the leg is very long. The hind foot is uncom- monly long, on which, to appearance, are placed three toes, the middle toe by much the largest and the strongest, and looks some- ‘thing like the long toe of an ostrich. The outer toe is next in size; and what appears to be the inner toe, is two inclosed in one skin or covering. The great toe muil much resembles that of an ostrich, as also the nail of the outer toe; and the inner, which appears to be but one toe, has two smali nails, which are bent and sharp.t * [Hunter appears to have taken this description from a skull in which the first deciduous molar was still retained. The total number of molares which are developed in the jaws of a kangaroo are seven on each side of each jaw; the greatest number in use at any given time is four on each side of each jaw; a posterior or fifth molar may be visible above the socket in the dry skull, but it does not cut the gum for use till the anterior one is pushed out. The succession of the molares is from behind forwards in both jaws. The first deciduous molar, upper jaw, resembles the first permanent false molar in the potoroo; it is elongated, compressed, and traversed by a longitudinal sharp middle ridge, at the internal base of which are three small tubercles. It is for cutting rather than bruising. ‘The corresponding tooth, lower jaw, is similar in form, but smaller, and has one tubercle in the posterior part of the inner side of the base. In some species of kangaroo, as the Macropus elegans, the false molar is permanent, but its earlier loss in Maer. major does not warrant a generic dis- tinction. ‘The second deciducus molar has the form of the ordinary grinders, but is smaller; it is shed before the first. The third is similar, but somewhat larger; and so also of the fourth: this grinder is much worn in old skulls, and in the lower jaw is lost, leaving then only ae molares inaged individuals.. The fifth, sixth, and seventh follow each other from behind forwards, and are of equal size. Before the fourth grinder is in place the permanent incisores are gained ; these closely resemble their predecessors, but are somewhat larger. In the Macropus major the exterior incisor upper jaw presents two inflected folds of enamel; these are wanting in the corresponding teeth of the smaller species, which retain the spurious molares.] | t [At a still earlier period the fore legs, following the usual law of develop- ment, exceed the hind legs in length.] + [Each of these toes has it proper metatarsal and phalangeal bones.] E](https://iiif.wellcomecollection.org/image/b33292292_0481.jp2/full/800%2C/0/default.jpg)
