^54 



BRAINS OF RATS AND MEN 



The electrically excitable cortex of the opossum 

 has been mapped by a number of physiologists. Gray 

 and Turner (1924) secured the results indicated on 

 Figure 37. It will be noted that the excitable cortex 

 does not coincide with any of the microscopically de- 



o.porb 

 fs.orb. 

 Q.prorb. 



o.temp. 



Q.strA 



b.rh. 



Fig. 36. — Topographic chart of the lateral aspect of the cerebral 

 hemisphere of the opossum, showing the arrangement of the structurally- 

 distinct areas. Two and one-half times natural size. After Gray (1924). 

 The rhinic fissure {fs. rh.) marks the boundary between the neopallium 

 above and the pyriform cortex below. 



termined areas. Nor is the excitable cortex of the 

 skeletal musculature in the preorbital area (Fig. i^Gy 

 a, prorb.) in front of the orbital fissure, an area which 

 corresponds in position and structure with Brod- 

 mann's area gigantopyramidalis (precentral or Ro- 

 landic cortex of man). On the other hand, the arm 

 area (points 1-4 of Fig. 37) lies in or near the postor- 

 bital area (Fig. i^G^ a. porb.)^ which in structure and 



