120 PRACTICAL ANATOMY. 



tion of others in making further examinations during the winter, but the reprints 

 of my paper were too long delayed, and the dissecting season was passed before 

 I could communicate with anatomists and make the necessary arrangements and 

 have the benefit of the results of the examinations of other subjects." 



THE COVERINGS OF THE BRAIN. 



Those structures intervening between the brain and the outside are brain pro- 

 tectives,and may be called coverings. In number they are three ; in a collective 

 sense, outer, middle, inner. The outer is called the scalp ; the middle, the cal- 

 varium ; the inner, the meninges. As above intimated, each of these three cov- 

 erings is a collective noun, and must be reduced, analytically, to its simplest 

 terms of individual structures. 



The scalp consists of the following layers : 



1. The skin, covered by a thick growth of hair in primitive man. 



2. The superficial fascia, the distribution area where you are to find all the 

 arteries, veins, nerves, and dermal muscles of the scalp. 



3. The occipito-frontalis muscle, consisting of an anterior and a posterior 

 belly, connected by a broad aponeurosis that takes the name of the muscle. 



4. A subaponeurotic layer of connective tissue, which you can account 

 for by consulting a paragraph in the introductory chapter on the non-apposition 

 of anatomical structures. 



There are, then, four layers. The scalp moves freely. The fibrous covering 

 of the bone is periosteum, and its subperiosteal connective tissue does not differ 

 from like tissue found underlying periosteum everywhere. These two structures 

 do not form integral parts of the scalp because they do not move. 



Dissection. Remove the skin having shaved the head by making cross- 

 incisions on the mid-top of the head, thus -f-. 



In the superficial fascia of the scalp you are to find the following structures : 



1. The supraorbital nerve and vessels. (Figs. 16 and 18.) 



2. The temporal branches of the seventh nerve. (Fig. 16.) 



3. The auriculo-temporal branch of the fifth nerve. (Fig. 16.) 



4. The temporal arteries superficial and veins. (Fig. 18.) 



5. The great occipital nerve second cervical, posterior division. (Fig. 22.) 



6. The small occipital nerve cervical plexus. (Fig. 22.) 



7. The great auricular nerve cervical plexus. (Fig. 22.) 



8. The posterior auricular artery branch of the external carotid. 



9. The posterior auricular nerve branch of seventh cranial. (Fig. 16.) 

 The above structures you have already found in your dissection of the face 



and neck. 



10. The dermal muscles are as follows (Fig. 14) : 



1. Musculus attrahens aurem draws the ear forward. 



2. Musculus attollens aurem draws the ear upward. 



3. Musculus retrahens aurem draws the ear backward. 



They have origin and insertion as indicated in the figure. They are insig- 

 nificant, and can only be demonstrated in some cases. The function of these 

 muscles is seen in some of the domestic animals the dog, horse, and mule. 



The occipito-frontalis (Fig. 14) has a posterior attachment to the outer two- 

 thirds of the superior curved line of the occipital bone and to the mastoid process 

 of the temporal bone. This muscular belly terminates anteriorly in a broad epi- 



