68 ON THE CUTANEOUS PIGMENTARY SYSTEM OF THE FROG 
PATE, Ti 
illustrates the anatomy and physiology of the cutaneous pigmentary system of the frog. 
Figs. 1 and 2 are sketched from webs of different feet of the same animal. The creature was dark when 
it was killed, but one of the legs afterwards underwent the usual post mortem change to a pale 
colour, and such was its state when Fig. 2 wasdrawn. The other limb was deprived of the power 
of thus altering by immersion for half a minute in chloroform ; and Fig. 1 shows the appearance 
of the colouring matter in the permanently dark condition of the integument. 
ty 
gq 
. 3 represents two chromatophorous cells with the pigment-granules fully diffused, the animal having 
been at the time coal-black. The bodies of the cells are seen to be pale, containing chiefly colour- 
less fluid, while some of the finest branches of the offsets are quite black, in consequence of the 
dark molecules being closely packed together in them. In the same figure a capillary fully 
distended with blood-corpuscles is also given. 
Fig. 4 represents the colouring matter in the same two cells during the progress of the process of con- 
centration. The dark molecules are already for the most part collected about the middle of 
the body of each cell; but in the very centre of each cell is a pale point, where the granules seem 
not yet to have insinuated themselves between the cell-wall and the nucleus. The same capillary 
is here seen much reduced in calibre. 
Fig. 5 shows the pigment in the lower of the two cells, concentration being still further advanced. 
In Fig. 6 the process is seen to be almost absolutely completed, the molecules being almost all of them 
aggregated into a black circular mass, occupying the middle of the body of the cell, the more 
circumferential parts of which contain only colourless fluid, and are therefore invisible. 
Fig. 7 is an outline of the wall of a large blood-vessel, with chromatophorous cells in its external coat. 
The pigment is almost completely concentrated, but the form of the section of the black masses, 
where they are seen edgewise, shows that they are not spherical, but disc-shaped. 
Figs. 8, 9, and 10 are drawn, with a much higher power, from young frogs, with small pigment-cells : 
they exhibit especially the form and relations of the nucleus. 
In Fig. 10 the pigment is shown in an unhealthy state, the molecules being irregularly aggregated. 
