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in the skin is directly influenced by the sympathetic nervous system. 

 If in a turbot tlie connecting brandies of some spinal nerves or 

 these nerves themselves, in that upward turned half of the body 

 containing the eyes, are cut through, there appears on the skin a 

 more or less sharply defined dark zone. Pouchet considered this 

 phenomenon to be caused by a paralysis of the pigment-cells in 

 consequence of the section of the nerves, and he called the dark 

 zones appearing after section, "paralytic" zones. He made however 

 no further researches as to the significance of these zones, when 

 considered as innervation-areas of sympathetic ganglia, and since, 

 to my knowledge, nobody has taken up again these yet so extremely 

 interesting researches. I have done so at the present time, and added 

 unto this a comparative investigation about the sensible innervation 

 of the skin. 



For objects I got numerous specimens of Solea (impar, vulgaris, 

 monochir) and Rhomboidichthys (mancus sen podas). This latter 

 species in particular, and likewise Solea impar, have furnished me 

 with excellent results, and the more detailed demonstration is prin- 

 cipally based on experiments made on these animals. The operative 

 part of these experiments was very simple. By a longitudinal incision, 

 cleaving skin and muscles, and passing along the lateral line of the 

 organ of sense in the ventral portion of the skin of the caudal pari 

 of the pigmented half of the body bearing the eyes, the origins of 

 a few haemal vertebral spinous processes were laid bare and the 



Fig. 1. 

 Scheme of course and distribution of the main trunks of the spinal nerves in 

 the caudal portion of the Pleuronectidi (taken from a preparation of Rhombus 

 laevis), 1, body of vertebra, 2, neutral spinous process, 3, haemal spinous process, 

 4'</, 4"(/, i'v, i"v, first and second longitudinal septum of the dorsal and ventral 

 muscles, — cr, ca, cranial and caudal boundaries of the preparation. — r.d., r.m., 

 r.v., ramus dorsalis, medius and ventralis of the spinal nerves — r.c.d., r.s., ramus 

 comunicans and ramus spinosus of the dorsal nerve-truuks. — r.c.s., left sympathetic 

 connecting branch. 



22* 



