CRANIOCEREBRAL TOPOGRAPHY. 



37 



cerebral surface (in cases of cerebral abscess, tumors, and operations upon the cortex), the surgeon 

 needs certain lines as aids in the localization. In consequence of the manifold variations in the 

 shape of the skull, these lines are not absolutely accurate in all cases, but they nevertheless furnish 

 indispensable guides. An exact topographic localization is never possible until the surgeon has 

 made an extensive opening in the skull and exposed the cerebral surface. Kronlein recommends 

 the following lines (see Fig. 13): 



FIG. 13. Craniocerebral topography (after Kronlein and Froriep). Explanation in the text. 



1. The base-line (horizontal line, ear-orbit line) through the infraorbital margin and the 

 upper border of the external auditory meatus (Reid's base-line). 



2. The superior horizontal line through the supraorbital margin, parallel to the base-line 

 (line of Kronlein). 



3. The anterior vertical line, at right angles to the base-line at the middle of the zygoma. 



