190 Mr Goodsir on certain Peculiarities in the 



fluid exuded, and its bulk was considerably diminished. When 

 boiled, it dissolved into a gelatinous mass, which passed in the 

 form of a clear transparent liquid through flannel. A few 

 shreds of animal matter remained. This fluid on cooling 

 became a fine jelly, inodorous and tasteless. The greater part 

 of this tissue, then, is composed of, or may be converted into, 

 gelatine.* 



When thin sections were examined under the microscope, 

 it was found to consist of a congeries of cells, which exhibited 

 all the characters of true primitive cells, each containing its 

 own nucleus, and the latter a number of minute nucleoli. 

 These cells were all spherical, or rather belonged to the order 

 of spherical cells, for they appeared occasionally, when much 

 crowded together, to be flattened at the points of contact, so 

 as to assume the dodecahedral form. After careful examina- 

 tion, 1 could detect no fat globules either in the interior of the 

 cells or in the spaces between them They appeared to be 

 filled with a transparent fluid, which, in individual cells, re- 

 fracted the light with great brilliancy. The cells adhered 

 very firmly, a circumstance which accounted for the peculiar 

 toughness of the tissue. Bloodvessels were detected in some 

 of the sections, but they assumed the appearance more of in- 

 tercellular spaces than of true vascular canals. Not having 

 any efficient micrometrical apparatus at the time, I could only 

 judge of the size of the cells by comparing them with human 

 blood-globules. I by this means ascertained that the cells in 

 £he gelatinous tissue of the sun-fish were about a third larger 

 than human blood-globules, that is .000332 to .000505 of an 

 inch. 



There was no trace of dermis or true skin, the coloured la- 

 mina of the integument appearing to be merely the superfi- 

 cial layer of the peculiar cellular tissue, changed by the de- 

 position of colouring matter in the cells to adapt it to its pro- 

 per function. The peculiar tissue must either be looked upon 

 as the true skin itself, or more correctly it must be considered 

 as the primitive nucleated vesicular tissue of the embryo fi h, 



* I am indebted to Dr Atkeu for this account of the chemical consti- 

 tution of the tissue. 



