2 APPLIED ANATOMY. 



arrangement of the fibres is shown in Fig. 3. Fibres starting from the point A not 

 only pass directly down to B, but also to each side to the points C and D. In the 

 same way, fibres starting from B not only pass upward to A, but also forward to E 

 and backward to F. Now, if the skin is moved in the direction of the forward arrow, 

 the fibres E B and A D are tightened and drag the aponeurosis forward. If the skin 

 is moved in the direction of the backward arrow, the fibres A C and F B are tight- 

 ened and so drag the aponeurosis backward. Thus it is seen that the aponeurosis 

 must follow the movements of the skin. 



The occipitofrontalis muscle with its aponeurosis arises from the supe- 

 rior curved line of the occiput and is inserted into the skin of the frontal region. 



Skin 



iuperficial fascia 

 Aponeurosis 



iS*^/Subaponeurotic connective tissue 

 VxPericranium 

 * Subpericranium 



kull 

 Dura mater 



Merkel describes the epicranial aponeurosis as dividing into two layers, one inserting 

 into the skin and the other into the rim of the orbit (Hand, der top. Anat. Bd. i, p. 

 17). The bellies of the muscle are comparatively short, about 5 cm. in length, the 

 remaining tissue extending between them constituting the aponeurosis. As it comes 

 downward from the temporal ridge, over the 

 sides of the head, the aponeurosis becomes 

 thinner and gives attachment by its superficial 

 surface to the anterior and superior auricular 

 muscles. It then proceeds downward to be 

 attached to the upper edge of the zygoma. 



Skin 



Aponeurosis 



FIG. 3. Diagram illustrating the method of attach- 

 ment of theskin to the aponeurosis of the occipitofrontalis 

 muscle. 



FIG. 4. Showing now the periosteum in 

 childhood dips between the bones in the line of 

 the sutures. 



Contraction of the occipitofrontalis muscle causes the skin of the forehead to wrinkle 

 transversely. It is a muscle of expression, and blends with the pyramidalis nasi 

 and corrugator supercilii. It is supplied by branches of the facial nerve. 



The subaponeurotic tissue is very loose and abundant, so that it does not tend 

 to confine the movements of the scalp, but favors them. Hence the scalp is readily 

 torn loose from the skull in scalping, machinery accidents, etc. This tissue is so 

 loose that effusions accumulate here and spread extensively. It contains only a few 

 blood-vessels. 



The pericranium in its normal condition is a thin, tough membrane containing 

 few blood-vessels. Except at the sutures, where it is firmly attached and dips 

 down between the bones, it is comparatively easily stripped from the skull and 



