( 315 ) 
Accordant to the Ist fact mentioned above, each marginal area 
must at least possess a breadth =<; as long however as the marginal 
area does not reach a larger breadth than is expressed by «+ y, 
the following view may be accepted: 
The insensible area (e.g. in fig. 11 and fig. 12) is the total of 
both central areas of the sectioned roots, but because they overlap, 
the total must be diminished by three times the central-area-over- 
lapping y, which they give one another reciprocally, and receive 
from the two neighbouring central areas. 
Thence the insensible zone produced by sectioning two roots is 
2X (@+2y)—3y=2x+y, and it it is proved experimentally 
that the sensible area is equivalent to the insensible area, then 
Bel ey Must be == Ary or tr — yx, 
This holds good only, if the marginal area does not exert a 
narrowing influence on the insensible area, which may only occur 
when the former is larger or equivalent to 24 + y — in our case 
equal to the central area. ‘The marginal area however, must 
possess a minimum breadth x. For our purpose the marginal area 
hitherto possesses only any value, because it must supply, together 
with another neighbouring marginal area, the sensation for the 
band x. For the rest it may even extend '/,y farther, but there 
it even may have a sensation-value so low under the threshold, that 
even the assistance of a second marginal area cannot enable it 
to be sensible. 
If the marginal area extends only until z is overlapped, the derm- 
atoma overlap one another for °/;, if however it extends to a breadth 
of «+ '/,y, then they overlap one another for */;. The central areas 
always overlap one another for 1/3, if the analgetic area is equivalent 
to the sensible area. In this case the dermatomata are ranged in 
such a manner, that the first does rest against the fourth, the 2nd 
against the 5t, the 34 against the 8th. This is represented in 
Fig. 16, and above each dermatoma its curve of sensibility has been 
indicated. 
The thick line represents the threshold that must be passed to 
make any sensation possible. (fig. 16 B). 
By addition of these curves, as is done in fig. 16 C, the curve of 
sensibility along the mid-dorsal line has heen expressed, representing 
a schema of sensation, by means of which may be calculated directly, 
what breadth sensible and insensible areas ought to possess with 
different sectionings. That the destroying of one dermatoma does 
not necessarily cause loss of sensation, is shown by the dotted 
line a, remaining above the threshold-line; whilst by the interrupted 
