LOCOMOTION OF MAMMALIA. 63 



tlie cartilage of the ala nasi, the outer and longer strip to the 

 skin of the upper lip near the nose, and becoming blended with 

 the orbicularis and levator labii proprius. The ' triangularis nasi/ 

 or ( compressor iiaris,' figs. 29, and 30, n, arises from the maxillary 

 external to the incisive fossa : its fibres proceed upward and 

 inward, expanding to an aponeurosis continuous, over the bridge 

 of the nose, with that of the opposite muscle. The f depressor alre 

 nasi ' is a short flat muscle radiating upward from the myrtiform or 

 incisive fossa of the maxillary ; it sends upper fibres to the septum 

 and back part of the alse nasi and lower ones into the orbicularis 

 oris. The ' orbicularis palpebrarum,' fig. 29, o, surrounds the 

 orbit and eyelids : it arises from the internal angular process of 

 the frontal, from the nasal process of the maxillary, and by a 

 short tendon at the inner angle of the orbit. It rapidly expands 

 to form a broad thin elliptical plane of fibres : the palpebral por- 

 tion is thin and pale : the orbital portion is thicker and of a 

 reddish colour. The action of the muscle is that of a sphincter, 

 the curved fibres in contraction approaching the centre : but as 

 thcv are fixed at the inner side the skin to which the muscle is 



*/ 



attached is drawn toward the nose, and becomes corrugated into 

 folds which converge toward the inner canthus. The ( comiffator 



O o 



snpercilii, is a small triangular muscle placed at the inner end of 

 the eyebrow, arising from the same end of the superciliary ridge : 

 its fibres pass upward and outward to be inserted into the under 

 surface of the orbicularis palpebrarum. It depresses the eye- 

 brow, and, in conjunction with its fellow, throws the integuments 

 into vertical folds as in the act of frowning. The 'occipito- 

 frontalis ' consists of an anterior and posterior carneous expansion 

 united by a broad f epicrauial,' aponeurosis. The anterior muscle, 

 fig. 28, f, consists of two lateral portions, each connected in- 

 feriorly with the integument of the corresponding eyebrow, and 

 slightly overlapped by the ' orbicularis.' The posterior or oc- 

 cipital portion, ib. o, also consists of a pair, attached inferiorly to 

 the upper curved line of the superoccipital, and to the mastoid. 

 The fibres are parallel and nearly vertical. The action of this 

 muscle is most apparent upon the skin of the forehead and the 

 eyebrows : it raises the latter and throws the former into trans- 

 verse wrinkles. 



202. Locomotion of Mammals. In the movements of the 

 human frame the three kinds of lever are exemplified. Those of the 

 head upon the atlas are on the principle of the first kind, fig. 31, 

 in which the fulcrum F is between the power p and the resistance 

 w. When the body is raised on tip-toe by the action of the 



