38 TOPOGRAPHIC AND APPLIED ANATOMY. 



4. The middle vertical line, at right angles to the base-line from the condyloid process of the 

 mandible. 



5. The posterior vertical line at right angles to the base-line from the most posterior portion 

 of the base of the mastoid process. 



If the point of intersection of the anterior vertical with the superior horizontal line is connected 

 with the point where the posterior vertical line strikes the vertex [that is, the antero-posterior 

 median line of the vertex. ED.], we have: 



6. The linea Rolandi, corresponding to the fissure of Rolando. 



If the angle formed by the superior horizontal line with the line of Rolando is bisected and 

 the bisecting line is extended to the posterior vertical line, we have : 



7. The linea Sylvii, corresponding to the fissure of Sylvius. 

 The following is an explanation of the letters in Fig. 13: 



K, Junction of the horizontal with the vertical limb of the fissure of Sylvius. 



S, Upper end of the fissure of Sylvius. 



R, Lower end of the fissure of Rolando. 



K and K', indicate the two trephine openings of Kronlein for the anterior and the posterior 

 branches respectively of the middle meningeal artery (see page 29). The rectangle ABK'M 

 corresponds to the area resected by v. Bergmann as a preliminary step to operative measures 

 in the middle cerebral fossa. 



QUESTIONS. 



How should the frontal sinus be opened in order to reach its communication with the nasal cavity ? 



What fontanelles are felt in the head of the new-born ? 



How may subcutaneous emphysema be produced after the frontal sinuses have been opened ? 

 . To what extent may the withdrawal of blood from the scalp from behind the ear, for example 

 aid in diminishing increased intracranial blood-pressure ? 



Which cranial nerves are, as a result of their course, particularly apt to be affected in basal frac- 

 tures and compressed against the base by tumors ? What is characteristic of this course ? 



From what situation in the face is it possible to wound the brain without a concomitant injury of 

 the cranial bones? 



Is the escape of blood or cerebrospinal fluid from the nose, in cases of basal fractures, of any value 

 in localizing the seat of the fracture ? If not, why ? What vessels may be involved ? 



Where are the places at the base of the skull which are pushed against the brain by tumors growing 

 from the sphenoidal sinus or from the ethmoidal cells ? Find these places in the illustrations. 



What difference exists between the skin of the scalp and the scalp proper, and how is the mova- 

 bility of both affected by their anatomic structure ? 



Why is it that cutaneous wounds of the scalp do not gape while wounds involving the entire 

 scalp do ? 



Why is it impossible to close large cutaneous defects in the scalp by uniting the edges of the wound ? 



What are the characteristics, dependent upon anatomic structure, of an effusion of blood or of a 

 suppuration in the scalp ? Beneath the scalp ? 



Why does the skin of the scalp bleed more profusely after injury than that of any other cutaneous 

 area ? Why do large flaps in this situation adhere more readily than elsewhere ? 



