1910-11.] Topography of Cerebral Cortex of Guinea-pig. 
405 
Type II. ( x x x ) in front of Type I. 
Depth of cortex varies from 1*5 mm. to 1*6 mm. 
1. Zone I. 
2. A narrow zone of angular and pyramidal cells. 
Fig. 4.— Type II. xlOO. 
3. A very indefinite granular zone — the granular layer of Bolton. 
4 and 5. These two zones may be considered as one broad zone of 
pyramidal-shaped cells. The cells, more especially in the deeper parts of 
the zones, are large and clearly defined, varying in length from 30 to 40 /jl 
and 12 to 20 fi in breadth. In a cursory examination of this cortical area 
