398 Anatomy Applied to Medicine and Smgery. 



in front. (2) The occipito-frontalis muscle is composed 

 of two parts, the occipital and the frontal the former 

 from the outer two-thirds of the superior curved line of 

 the occipital bone and from the ridge on the mastoid ; into 

 the epicranial aponeurosis, one and a half inches from its 

 origin the latter from the front portion of this epicranial 

 aponeurosis, into the deep surface of the skin of the eye- 

 brows and the root of the nose. Nerve sup- 

 ply. The facial, through its posterior auricular 

 branch supplies the occipital portion, while the tempero- 

 facial branch of the same nerve supplies the frontal por- 

 tion. Action. The occipital part draws back the apon- 

 eurosis and with it the scalp, while the frontal portion, 

 when its insertion is fixed by the contraction of the orbi- 

 cularis palpebrarum, draws forward the scalp. Simul- 

 taneous action of the two parts of this muscle elevates the 

 skin of the forehead into ridges, as seen in the expression 

 of horror, etc. Contraction of the frontal portion, alone, 

 produces the wrinkles of the forehead indicative of a more 

 moderate degree of expression, as surprise, etc. (3) 

 Delicate areolar tissue, which is almost devoid of fatty 

 particles, loosely connects the epicranial aponeurosis to the 

 pericranium beneath. The laxity of this union between 

 the epicranial aponeurosis and the pericranium allows the 

 former to glide easily over the skull, permitting, therefore, 

 great freedom in the movements of the occipito-frontalis 

 muscle and thus assisting in preventing the effects of 

 such injuries to the skull as result from blows, etc., by 

 causing the instrument inflicting them to glance, the more 

 readily, off the skull. (4) The pericranium, or periostea! 

 covering of the bones of the skull, is loosely attached to 

 these bones, excepting at their margins, where it blends 

 with the upper portion of the sutural membrane situated 

 between the bones, and, since the dura mater is adherent 



