March 1, 1892.] 



KNOWLEDGE 



47 



which is always of especial value as being that part of the 

 organism which is usiiall}- alone preserved in a fossil state. 

 Let us then first turn our attention to the skeleton of these 

 animals , of which we may see examples in our larger museums. 

 The most remarkable feature noticeable in such a skeleton 



Fig. 1. — Skeleton of the Siberian Jlnmmotli. with the skin still attached to the skull 



(From Jardine.J 



(Fig. 1) is that the various long-bones of the limbs are placed 

 almost directly one above another, so as to form nearly 

 vertical columns of support for the body ; whereas in 

 ordinary Ungulates, such as a horse or an ox, these bones 

 are set very obliquely to one another, iloreover, as a similar 

 vertical position of the limb bones occurs in several old 

 extinct Ungulates which are known to be of extremely 

 primitive organization, we may take it that an Elephant's 

 limbs are likewise of a primitive type. ■ We have, however, 

 further evidence in confirmation of this primitive structure. 

 Thus Elephants differ from all other living Ungulates in 

 having five complete toes to all their feet (Fig. 2). More- 

 over, whereas in other liv- 

 ing Ungulates (except the 

 little Hyrax) the bones of 

 the wrist are not situated 

 in vertical rows imme- 

 diately over the metacarpal 

 bones of the foot, but, on 

 the contrary, cross and 

 overlap one another, in 

 Elephants they have the 

 former relation, with the 

 single exception that the 

 bone marked / o\ erlaps the 

 Fig 2 —Bones of the left fore foot one lettered td to a certain 



of an . Elephant, ^ natural 



The lettered bones are those of the 



extent. This difference 



wrist or earpus, and the numbered '^^J ^^ illustrated by 

 ones the metacarpals, below which saying that if we were 

 are the bones of the toes.— [After to take 'a hatchet and 



0^^°"') chop verticaUy upwards 



between the third and fom-th toes of an Elephant's 

 foot there would be nothing to resist the passage of 

 the blade till it reached the bones of the leg, whereas 

 in all other Ungulates — the pig, for instance — the 

 blade could not pass through the wi-ist without cleaving 



solid bone. Again, whereas ordinary Ungulates walk solely 

 on the tips of their toes, and are thus termed digitigrade, 

 while the bones of the toes themselves are more or less 

 elongated. Elephants walk on the soles of their feet in the 

 so-called plantigrade fashion, and have very short toe 

 bones. Now since all the large 

 extinct Ungulates of the Lower 

 Eocene or earliest Tertiary period 

 also have five-toed feet, very 

 similar to, but still shorter and 

 of even simpler structure than 

 those of Elephants, there can be no 

 doiabt as to the extremely primi- 

 tive plan on which the entire limbs 

 of the latter are constructed. As 

 regards, therefore, its limbs and 

 feet, an Elephant may be said to 

 be an essentially old-fashioned 

 animal. 



If, however, wc turn to their 

 teeth we shall find that Elephants 

 are very far indeed from being of 

 a primitive or old-fashioned type ; 

 the truth being that they are, on 

 the contrary, very peculiar and 

 specialized in this respect. The 

 first and most obvious peculiarity 

 in regard to their dentition is to 

 be found in their tusks, which 

 correspond to one of the pairs of 

 upper front teeth in man, and 

 also to the single pair of such 

 teeth in the Rodents (rats, hares, 

 itc). Moreover, these teeth, like the incisors of the 

 Eodents, grow continuously throughout the life of the 

 animal, owing to the circumstance that the pulp- 

 cavity at their base always remains open, and has a 

 permanent connection with the soft structures of the 

 gum. In our own teeth, on the contrary, the pulp-cavity 

 closes at a certain period, after which there is a total 

 cessation of growth. These ever-growing tusks of the 

 Elephant, are preceded in the young animal by a pair 

 of small milk-tusks, with a closed pulp-cavity, which 

 are shed at an early period of life. In both of the 

 li\-lng species of Elephant the tusks are confined to the 

 upper jaw ; but whereas they occur in both sexes in the 

 African Elephant, in the Indian species large permanent 

 tusks are restricted to the male, and are not, indeed, invari- 

 ably present in all individuals of that sex. The primitive 

 Elephants, or Mastodons, frequently, however, had tusks 

 in both the upper and lower jaws ; and since these did not 

 generally attain the huge dimensions which they reach in 

 many true Elephants, it is evident that in this respect 

 the Mastodons departed less from the ordinary type of 

 Mammals, where the front teeth are not greatly larger 

 than the hinder ones, and those of tlie upper and lower 

 jaws correspond with one another in size and number. 

 Before leaving the subject of tusks, it may be mentioned 

 that the ivory of which they are composed differs from the 

 so-called ivory of other teeth in a manner which renders it 

 always easy to determine whether a reputed ivory article 

 is genuine. This peculiarity consists in the circumstance 

 that a transverse section of a tusk exhibits a series of fine, 

 decussating, curved lines radiating from the centre to the 

 circumference, and forming curvilinear lozenges at their 

 intersections. This pecidiar structure is in fact precisely 

 similar to the " engine-turning " on the back of a watch ; 

 and in an ivory knife-handle it should be distinctly \dsible 

 at the butt. {To be continued.) 



