( 521 ) 
At the mid-dorsal line (Fig. 28A) 2 is represented in caudo-cranial, 
y in cranio-caudal direction. 
If this is supposed to be the positive direction, then in the case 
of central areas being ranged in wide intervals from one another, 
as they are at the mid-ventral line, there will only be this difference, 
that y will be set like « in caudo cranial direction, consequently y 
will be set in negative direction. (Fig. 28 B) The breadth of the 
ventral central area thus becomes «—2y, that of two succeeding 
central areas 2e—3y, three 3e—4y etc, whilst the breadth of 
Fig. 28. 4. General representations of the ranks of the central areas at the mid- 
dorsal line, k=x-+2y. B. of the ranks of the central areas at the mid- 
ventral line, k=x —2y. C. of the ranks of the central areas at the lateral 
part of the body, k = 2y —x. 
the insensible bands may be represented by rz, 22—y, 3«—2y etc. 
according to the number of sectioned roots. 
