422 SAMUEL C. PALMER 
From tables 4 to 7 it will be seen that the rods are generally 
more numerous per unit field than the cones and double-cones. 
Exceptional cases exist, however, where the cones are found 
to be more numerous than the rods (table 4, nos. 16 7, 33 1, 40 1), 
and I am convinced after examination of a great number of retinas 
that such areas are not infrequent in every one of the five regions. 
The actual relative values of rods, cones, and double-cones and 
the total average number per unit fields, as well as the total average 
number per five unit field, are given in table 6, where the rods 
consistently outnumber the cones. In table 7 I have brought 
together many data for the visual cells. Between the maximum 
and minimum retinas there is a variation of 25.per cent, at least, 
in the total number of visual cells. 
TABLE 5 
Average number of retinal elements per unit area in right and left eyes 
i] | 
5 | AVERAGE NUMBER OF | MAXIMUM NUMBER OF | MINIMUM NUMBER OF 
Pp — —~ — — = os 
Ho » oO ~ Eo] 
Seidl N= ee | 25 = a no = a So 
SIDE EXAMINED Sis i fe 5 | gx = = aa g 2 ae 
<5 e ke |} os ke oS & Seat 
ie 5 2 rae 5 S $4 Be lie ice $a 
<8 Py nz Pie Ml) ices am | = eace) ang | ae 
ad ne oo Qn Tr o- Qn ns on Qn 
ast ao qe 30 Lom} qo 30 av qo 350 
zm ow os on ow oe on own on on 
p [on] '@) Q foxy .S) (a) — Oo A 
; | |— hates 
| 
Richness. OLOLS M49 RZ Tose 2alelo 70.5 | 47 25 35 26 5 
Left 0.013 | 53 AL. | 12.7 | 70.5 49.5 25 Sine 28 8 
TABLE 6 
Average numbers of visual cells in the five selected unit areas (see table 4) 
AVERAGE NUMBERS OF THE SEVERAL KINDS OF 
RETINAL ELEMENTS PER UNIT AREA IN THE | AVERAGE 
POSITIONS OF UNIT FIELDS ery Sa oe | a libea peeks 
| : Double | Uncertain | UNIT ARBA 
Rods | Cones cones elements | 
Anterior...... en ee B70 | GALYOs VMS opens a 116.0 
Posterlonx..3\stontea bee 48.2 43.1 | 17.8 0.4 109.5 
Dorsal... 5. A, Tet Tete 43°56 |  v41¢0 lilies: 1.9 98.3 
Wentral’ ic. ccee en eee 59.5 | 41.9 | 11.0 ato |) ae 
BUN USt.c. coho ee Prete oe eA ee 36.2 15.8 0.8 99.0 
Total number of the several 
kinds of elements in five 
to 
bo 
combined unit areas....... 95b.4 |. 204.1 es 
8.7 | 540.4 
