THE MYOLOGY OF THE HEDGEHOG. 377 



The pelvis is remarkably spacious. The symphysial union 

 of the pubes is always small, and, sometimes, the bones remain 

 separate. The subpubic arch is much rounded. The ilium is 

 narrow, and a mere ridge separates the iliac fossa from the 

 gluteal surface. The femur has a round ligament, and a 

 prominent ridge represents a third trochanter. The distal 

 ends of the tibia and fibula are anchylosed together. 



One of the most notable peculiarities of the Hedgehog is 

 its power of rolling itself up into a ball, from all sides of 

 which the spines protrude. This is effected, for the most part, 

 by the contraction of the greatly-developed cutaneous muscle, 

 the chief fibres of which are disposed as follows : A very 

 broad band, the orbicularis pannieuli, encircles the body latr 

 erally. In front, it partly arises from the nasal and frontal 

 bones, and partly is the continuation of a thick mass of fibres 

 which pass over the occiput. Posteriorly, each lateral division 

 of the muscle spreads out into a very broad band, which is 

 thick ventrally and thin dorsally, and adheres closely to the 

 skin, from the line at which the hairy and spinigerous surfaces 

 join, to near the median line of the back. Posteriorly, the 

 two lateral halves of the orbicular muscle pass into one an- 

 other upon the distal half of the short tail. 



The action of this muscle will depend upon the attitude 

 of the animal when it contracts. If the head and tail are fully 

 extended, the orbicularis can only diminish the dimensions of 

 the spinigerous region of the skin and erect the spines. But 

 if the head and tail be more or less flexed, as they always are 

 in the ordinary attitude of the Hedgehog, the orbicularis will 

 play the part of a powerful sphincter, approximating the 

 edges of the spinigerous area toward the centre of the ventral 

 side of the body, and forcibly enfolding the trunk and limbs 

 within the bag thus formed. It is, in fac t, the chief agent in 

 coiling the body up, and keeping it so ceiled. 



Numerous muscular bundles take a 1 adiating direction on 

 the dorsal aspect of the body, and antagonize the orbicularis : 

 1. A pair of slender occipito-frontales arise from the occipital 

 crest, and are inserted into the integument over the frontal 

 and nasal bones. 2. A pair of occipito-orbiculares arise from 

 the same crest, and pass into the anterior part of the orbicu- 

 laris. 3. A pair of broader cervico-orbioulares arise from 

 Ihe fascia of the neck, and pass to the dorsal part of the an- 

 terior fourth of the orbicularis. 4. Slender dorso-orbiculures 

 arise close to the hinder ends of the trcqjezii and spread out 

 above the foregoing. 5. Two stout muscles, coccygeo-orbicu' 



