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VIII. — Oil the Connection of Nerves and ChromoUasis. 

 By M. Geokges Pouchet. 



Plate CVIII. 



Since we have shown by direct experiments the influence of the nerves 

 upon the pigment cells of the skin of fishes, and especially of the skin 

 of flat-fish (Pleuronectes maximus, Linn.), the relations between 

 these elements and the nerves naturally attract our attention. Herr 

 Kiihne [untersuchungen liber protoplasma] in 1864 figured the 

 larger connections between the nervous tubules covered with myehne, 

 and the connective cells of the cornea. But beyond that the iden- 

 tity of these cells and the pigment cells is not estabhshed further 

 than the doubtful effect of a reagent used by Herr Kiihne, nitrate of 

 silver, it does not appear that the conclusions of his memoir have 

 been definitely adopted by anatomists. 



The pigmentary cells or chromoblasts are situated below the 

 skin, which is represented in many fishes, as in the Batrachia, by a 

 dehcate hyahne membrane, about 19 to 20 Paris lines in thickness. 

 It is beneath the membrane properly so-called that the chromoblasts 

 are found mixed with other elements, which seem of a connective 

 tissue-like character. The chromoblasts themselves are essentially 

 composed of a mass of sarcodic substance (or protoplasm), usually 

 surrounding a nucleus, but being able probably to subsist without 

 it. In the midst of this sarcodic substance is deposited the colouring 

 matter, which is consequently a true pigment. This colouring 

 matter is of various tints, but generally it is, in the least refrangible 

 half of the spectrum, yellow, orange, red, brown, and black. Some- 

 times this colouring matter is hquid, and forms — as one sees it 

 in the embryos of Crustacea — a coloured drop in a portion of the 

 sarcodic substance near the nucleus. When it extends in its 

 amoeboid movements, it draws over it the coloured drops. 



At other times, and indeed most frequently, the colouring matter 

 is spread out in granulations throughout the mass of protoplasm, 



EXPLANATION OF PLATE CVIII. 



Enlargement x 1000. 

 Fig. 1. — Laminous elements of the membrane of the pectoral fin of a turbot, 

 4 centimetres long. In situ. 

 „ 1 bis. — Three laminous elements isolated. 

 „ 2. — Elements of the same membrane at another point. In situ. 

 „ 3. — Nervous fibre. 



„ 3 a. — Chromoblast -without nucleus in contact with a nucleus of nervous fibre. 

 „ 3 b. — Chromoblast in continuity with a nervous fibre. 

 „ 3 c. — Idem. 



„ 3 d. — Nervous fibre in continuity with a nucleus of a chromoblast. 

 „ 3 c. — Chromoblast in continuity with a nervous fibre. 

 ,, 3/. — Idem. 

 „ 4. — Nervous thread accompanying a capillary. 



