CHAP. IV] THE GENERAL ANATOMY OF THE LEMUROIDEA 77 



for the M. peroneus longus as to suggest that this muscle acts 

 here as an adductor of the hallux, thus strengthening the grasping 

 power of the foot. The hallux is long, and distinctly stouter 

 than the other digits. The terminal phalanges of all the digits 

 are very small in comparison with those situated more proximally : 

 the terminal phalanx of the second digit is tapering and spine- 

 like, and thus corresponds to the peculiar shape of nail which it 

 bears. 



F. Muscular System 1 . 1. The subcutaneous musculature. 

 This system of muscles is well developed about the head and neck, 

 as shewn in the accompanying sketch of a dissection (Fig. 42). 



Several divisions of the facial musculature can be recognized ; 

 and below the mandible, the cutaneous musculature is divisible 

 into a superficial (platysma) stratum and a deeper sheet corre- 

 sponding to the M. sphincter colli (cf. Ruge, quoted by Wiedersheim : 

 Structure of Man, p. 10G), Fig. 42. 



The dorso-humeral sheet is also well developed. 



2. Of the submental muscles, the digastric is perhaps the 

 most noteworthy. In appearance it resembles the corresponding 

 muscle in some of the Marsupialia (Macropus). The distinction 

 of an anterior and a posterior belly is barely perceptible. A 

 continuous muscular band extends from the occipital bone 

 forwards, to be attached to the deep surface of the body of the 

 mandible just in front of the foremost fibres of the masseter 

 muscle (the latter curves inwards round the lower margin of 

 the jaw). The stylohyoid muscle crosses the digastric super- 

 ficially. Near this place, the digastric has a tendinous strip 



1 The muscles are grouped in eight divisions bearing certain relations to the 

 functional characteristics and adaptations of the animal. These divisions are 

 defined briefly as follows: 



1. The cutaneous musculature, especially the " muscles of expression." 



2. The submental muscles, especially the M. digastricus. 



3. Muscles used in balancing the head or in moving that part. 



4. Musculature of the shoulder, as related to arboreal life and the correspond- 



ing mode of progression. 



5. Muscles of the arm and forearm in relation to prehension. 



6. Muscles of the digits of the hand. 



7. The diaphragm. 



8. Muscles of the pelvis and lower limb, in relation to the erect attitude. 



