1000 



INSECTIVORA. 



and the circumference exceedingly thick and 

 somewhat raised. To different portions of this 

 circumference of the muscular covering are 

 attached several accessory muscles. Anteriorly 

 there are two pairs ; one arising from the me- 

 dian line and inserted into the nasal bone ; the 

 other, more external, apparently confounded at 

 its origin with the external orbicular fibres, is 

 inserted into the side of the nose and incisive 

 bones. Posteriorly a pair of broad muscles, 

 of a pyramidal form, arise from the posterior 

 part of the fleshy circumference, and are in^ 

 serted into the side of the tail towards the ex- 

 tremity. 



On the ventral aspect there are also several 

 portions of muscle, belonging to the same ap- 

 paratus. There is one beneath the throat, aris- 

 ing from the anterior part of the thorax, under 

 the skin, and is inserted about the lateral parts 

 of the head near the ears. Another arises from 

 the median line of the sternum, and passes 

 obliquely forwards over the shoulders, in front 

 of them, to join the margin of the great or- 

 bicular muscle before described. There is 

 another ventral portion which has a very ex- 

 tended connexion. It is attached around the 

 anus, to the lateral parts of the tail and neigh- 

 bouring parts, extends over the whole surface 

 of the abdomen, and then divides into two 

 portions; one internal, and larger than the other, 

 passes under the axilla, and is inserted into 

 the superior and interior part of the humerus; 

 the other, external, passes laterally upwards, to 

 be inserted into the margin of the great or- 

 bicular muscle near the neck. The muscles 

 hitherto described lie superficially; but there 

 are others which are seated underneath the 

 great muscle of the back. One arises from the 

 side of the head, being attached to the meatus 

 auditorius on each side, and loses itself in the 

 anterior point of the orbicular muscle. There 

 is also a thin layer of fibres lying beneath the 

 great muscle, of which the anterior are attached 

 to the superior interior portion of the humerus, 

 and the posterior to the third ventral muscle 

 already mentioned. 



We have here a very extensive and a very 

 powerful apparatus, and it now becomes ne- 

 cessary to consider its application. When the 

 hedgehog is rolled up in a ball, it is com- 

 pletely enveloped, as regards all the upper and 

 lateral parts of the body, in the great orbicular 

 muscle. When once brought into this position 

 the simple contraction of the thick circum- 

 ference of the muscle, which forms a true 

 sphincter, is sufficient to retain it. If the ani- 

 mal unrolls itself, the disc of the great muscle 

 contracts whilst the circumference is relaxed, 

 allowing the exit of the feet and the uncover- 

 ing of the belly and sides: then the whole 

 muscle contracts together, and lies in a mass 

 on the back. By this universal contraction, 

 the necessary muscles become stretched, and 

 in a condition to perform their several offices ; 

 by the contraction of the anterior ones the head, 

 and by that of the posterior the tail, is raised, 

 whilst those which lie beneath raise the head 

 and neck together, and the animal is now 

 ready for progression. On the other hand, on 



the apprehension of danger, or wheti reposing, 

 it rolls itself into a ball by the following pro- 

 cess. The orbicular muscle relaxes, and the 

 muscles extending from it to the head and to 

 the tail extend it in those directions, whilst the 

 deap-seated transverse muscles which are at- 

 tached to the external lateral portions, and lie 

 on the belly, bring this part of the circum- 

 ference downwards. At the same time the 

 head is brought downwards towards the breast 

 by the ordinary flexion of the head, and by the 

 cutaneous muscles of the neck already de- 

 scribed; the tail and the hinder legs are brought 

 forwards under the belly, and the flexors of the 

 limbs contract. The great orbicular muscle 

 passes downwards over the sides, then contracts 

 at the circumference, and forms a sort of sac or 

 purse, enveloping the whole body and limbs. 



III. Digestive organs. It is, of course, in 

 the structure of the digestive organs, and par- 

 ticularly in that of the teeth, that we find the 

 distinguishing characters of the whole order; 

 yet so nearly do these organs in the Insecti- 

 vora approximate to those in the insectivorous 

 division of the Cheiroptera, that it would not 

 have been possible to separate the two groups, 

 had there been no other important points of 

 distinction. From the insectivorous Quadru- 

 mana they are distinguished by the planti- 

 grade character of the posterior extremities; 

 from the bats by the whole structure of the 

 limbs, and from all the true Carnivora by the 

 tuberculated teeth. 



There is no inconsiderable difficulty in as- 

 signing the various anterior teeth in the Insec^ 

 tivora to their proper classes. In most of the 

 genera, according to the statement of both the 

 Cuviers and others, there are no canine teeth, 

 and the false molares are very numerous ; but 

 it is in many cases doubtful whether the an- 

 terior false molares, as they are termed by 

 these anatomists, be not theoretically canines 

 modified in their form. On this point, how- 

 ever, there is no possibility of coming to a 

 satisfactory conclusion, as every one will at 

 last form his own opinion on each case; I shall 

 therefore follow the arrangement of Frederic 

 Cuvier as the most generally known, and, 

 upon the whole, by for the best authority on 

 the teeth of the Mammifera. 



The incisive teeth vary greatly in the dif- 

 ferent genera. In Mygalc, in Scalops, and in 

 Condytura, there is in the upper jaw but a 

 single incisor on each side, which is very strong 

 and of a triangular form. In the first of these 

 genera it is somewhat curved downwards and 

 backwards, and slightly resembles that of some 

 Ilodentia. In Snrex (fig- 449) it is also single, 

 very strong, curved, and similar to the canine 

 tooth in the Carnivora, but furnished with a 

 strong tooth-like process posteriorly, appearing 

 almost like a distinct tooth. 



In Talpa (Jig. 441) there are three superior 

 incisores on each side, which are small with 

 cutting edges, like those of the Carnivora. In 

 Chrysochloris (fig. 450), the single superior 

 incisor is curved, convergent, obliquely trun- 

 cate and pointed; and in Erinaccits (fig.45l) 

 there are three pairs, of which the first is large, 



