560 ZOOLOGY. 
result was observed. When the trigeminal nerve was severed, all 
of the pigment cells on that side of the head supplied by it were — 
paralyzed. The animal operated upon, kept in a tank with a sandy — 
bottom, had a faded color, only a small portion of the head rè 
mained dark, a smaller or larger portion, depending upon how 
large a part of the trigemimus was severed. A corresponding 
result followed the separation of the spinal nerves. The cowrsè 
of the severed nerve was followed by a dark colored stripe; ® 
the back of the pleuronectide, zebra-like lines were seen. There 
sultless severing of the spinal cord proves, that the influence that | 
a spinal nerve has upon the coloring cells does not pro 
the spinal cord. The splanchnic and sympathetic nerves are aged | 
brought into question. The severing of the former gives no result, 
If on the contrary the sympathetic nerve is severed anywhere on 
the inferior portion of the vertebral canal, paralysis of all of the : 
pigment cells of the skin occurs, posterior to the cut. op oF ; 
position of the fine delicate sympathetic nerve makes it impossible : 
to divide without injuring the neighboring parts. The i 
vives the operation two and three days. During this time it Gi i 
light and half dark colored. Similar trials made upon the ee 
maxillary nerve and artery, both of which lie superficially ane 
accessible, make it possible that the real nerve stem which reg fe | 
the movement of the pigment cells is not the one that aceon e 
the blood-vessel. Pouchet tried cutting the sympathetic nee” : 
its origin, behind the articulation of the suspensorium, borta 
_ such result as was anticipated. The length of time that i : B 
ysis of the pigment cells lasts, after the nerve is severed, . Me 
fully known ; it has been found to remain some weeks as mars” 
at first. The paralyzed portions upon the surfa pee 
ceive this mixed color, like the blind pleuronectida mar z 
light, according as the remaining portion of the skin is m yee: 
by the surroundings. Poisoning the fish with curare, $ 
morphine, veratria and sontonin has no especial influence | 
change of color. i that bad 
The influence of habit was marked. A pleuronectiðe ith 
lived a long time in a tank, the bottom of which was i fot | 
sand, when removed to one with a brown bottom, TORE — 
days before it fully received a corresponding color. 
Pouchet noted his observations daily, and came 
sion that the change of color is at times influenced, 
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to the coni 
put that 
