REGIONS AND MUSCLES OF THE CRANIUM. 



747 



I. Occlplto-frontal region. The anterior and 

 posterior boundaries of this region are suffi- 

 ciently obvious on the integuments, the eye- 

 brows forming the anterior, the posterior being 

 constituted by a line extending as far as the 

 mastoid process on each side of the occipital 

 protuberance corresponding to the insertion of 

 the superficial muscles of the back of the neck, 

 which protuberance can be felt through the 

 integuments. The lateral limits, however, are 

 not so distinct ; in the living subject, however, 

 when the temporal muscle is rendered tense, a 

 distinct line of demarcation is felt along the 

 upper margin of this muscle, extending down- 

 wards and backwards nearly as far as the mas- 

 toid process. 



We proceed to examine the several structures 

 which are presented to the anatomist as he 

 pursues the dissection of this region. 



1. Integument. It is in this region that we 

 can best examine the general characters of the 

 integument of the cranium, commonly known 

 under the name of scalp (Fr. cuir chevelu). 

 The greatest part of it is remarkable for the 

 more or less luxuriant growth of hair from it,* 

 the nature of which, it is hardly necessary to 

 observe, differs materially in the male and in 

 the female. In the natural state about two- 

 thirds or three-fourths of the scalp are covered 

 with hair, the anterior third or fourth, namely, 

 the skin of the forehead, being uncovered. 

 In front the hairs terminate abruptly on the 

 frontal region ; behind they terminate less ab- 

 ruptly, and descend in general to a variable 

 distance on the posterior part of the neck, 

 becoming finer and more downlike as they 

 descend. The natural direction of the hairs 

 is at right angles with that portion of the scalp 

 from which they grow; consequently the dif- 

 ference of direction of the hairs depends upon 

 the differences in the aspects of those regions. 

 This is most obvious in that part of the head 

 which is called the crown, which in most per- 

 sons inclines downwards and backwards to a 

 greater or less extent. Such, however, is the 



parietal, and occipito-mastoid. The advantages to 

 be derived from the subdivision of the body into 

 so many small regions as is adopted by the French 

 anatomists, are by no means obvious. I decidedly 

 prefer a subdivision which is indicated by certain 

 naturally prominent points or landmarks, which 

 will, 1 think, in general be found to map out 

 regions not too limited nor too numerous, nor yet 

 too comprehensive. 



1 We cannot resist the temptation of transcribing 

 the following passage from Gerdy, which is not 

 devoid of some national characteristics. *' La 

 surface superieure de la tete est arrondie et ovoide. 

 Elle est couverte par les cheveux qui en cachent 

 les formes, lui donnent, par la soupplesse et le 

 contraste de leur couleur, une sorte de beaute dif- 

 ficile a exprimer, et fournissent au gout delicat des 

 femmes I'ornement le plus gracieux et le plus se- 

 duisant par les masses legeres, les guirlandes flex- 

 ueuses, les boucles arronJies qu'elles en composent, 

 et par les mille arrangemens que suggere a leur 

 imagination 1'amour ou Fart de plaire. Mais la 

 tete, se depouillant avec 1'age, de la chevelure 

 qui 1'embellisait, ne presente plus dans la vieillesse 

 qu'une surface nue et luisante, ou Ton entrevoit 

 quelquefois la trace des sutures frontales et parie- 

 tales." 



influence of art in the arrangement of the hair, 

 that it is difficult to meet with " a head of 

 hair" to borrow the phrase from the hair- 

 dresser, where the growth is perfectly na- 

 tural. 



There is an obvious difference in the nature 

 of that portion of the scalp from which hairs 

 grow, and that which is naturally bald : the 

 former is much thicker and denser, owing, no 

 doubt, to a larger developement of the fibres 

 of the corion, and to the great magnitude of 

 the hairs which pierce it. It is at the posterior 

 part of the occipito-frontal region that the hairs 

 are strongest, and that portion of the scalp 

 very rarely becomes bald. 



2. Subcutaneous tissue. Subjacent to the 

 integument is a dense and lamellated^ cellular 

 tissue, with little fat, and such as does exist 

 deposited in small pellets, much more nume- 

 rous in the posterior part of the region. This 

 cellular membrane is very intimately connected 

 with those parts of the scalp especially from 

 which hairs grow ; it is much more loose and 

 less adipose in the frontal region ; it also ad- 

 heres pretty closely to the subjacent aponeurotic 

 expansion of the occipito-frontalis muscle. 

 The bulbs of the hairs are lodged in it. The 

 farm adhesion of this cellular membrane on 

 the one hand to the skin, and on the other to 

 the subjacent aponeurosis, is sufficient to ac- 

 count for the great pain and danger which at- 

 tend punctured wounds of the scalp, in conse- 

 quence of the non-extensibility of the membrane 

 and the tension which a very slight degree of 

 swelling consequently gives rise to. 



3. Muscles. If the scalp and subcutaneous 

 tissue be divided by a transverse incision over 

 the vertex, and the flaps carefully dissected off, 

 one as far as the eyebrows, the other to the 

 superior curved line of the occipital bone, the 

 occipito-frontalis muscle is brought into view. 

 Anteriorly and inferiorly we find the few fibres 

 of the orbicularis palpebrarum muscle overlap- 

 ping the occipito-frontalis just above the mar- 

 gin of the orbit. 



Occipito-frontalis (epicranius, Albin. : de- 

 scribed by some anatomists as two distinct 

 muscles, the frontal and occipital}. 



This is an expanded digastric muscle occu- 

 pying the whole of this region. The two bellies 

 of which the muscle is composed are united in 

 the centre by a broad aponeurotic expansion. 

 The anterior belly corresponds to a great part of 

 the frontal bone, and the posterior to a part of 

 the occipital. Very frequently the fibres are 

 weak and pale, so that the dissector finds it 

 difficult to trace out the extent and attachments 

 of the muscle ; and, moreover, even in its most 

 developed state it is a thin muscle, so that great 

 care is required for the accurate dissection of it. 



The anterior belly of this muscle, or that 

 which is by some called the frontal, consists 

 distinctly of two lateral portions united by a 

 narrow triangular slip of aponeurosis. Each 

 portion is connected inferiorly to the integu- 

 ment of the eyebrow through the intervention 

 of cellular membrane, and slightly overlapped 

 by the superior fibres of the orbicular muscle of 

 the eyelids, and commingled with some of the 



3 c 2 





