Structure of the Scales of Fishes. 281 



minarj- examination^ would have been altogether unintelligible. But we 

 are now in a condition^ on looking at any scale whatever, that of Corvina 

 nigra (fig. 9), for example, to understand the organization of these lines ; 

 we perceive that the lines derive their origin from the cells ; one of 

 their edges is still irregularly undulated ; they are prominent, raised 

 above the scale, and form the most salient points of it. We perceive be- 

 neath the bases of these lines deeper than the rest of the scale, and 

 placed lower than the lines. Of this we may easily convince ourselves 

 by the microscope, because, in order to get a good view of them, it is 

 necessary to change the focus, although sometimes only very little. With 

 regard to the corpuscles, we shall speak of them afterwards ; merely re- 

 marking, in the mean time, that, in the engraving alluded to, the scale is 

 presented in the position where the lines are in the focus, which prevents 

 the corpuscles from being distinctly seen. 



If we examine these lines near the terminal field, in scales which arc 

 provided with teeth, we perceive them often joined to the neighbouring 

 line by a curvature, which gives them the appearance of a line forming 

 the continuation of the other which is curved. We shall afterwards 

 speak of the form of these lines in the focus. 



We have thus arrived at a result very different from that come to by 

 tliose observers who consider these lines as nothing but the edges of the 

 layers of the scale. Such an opinion, which the slightest microscopical 

 inspection would oppose, for the reasons we have mentioned, is entirely 

 overthrown by our observations. We should have preferred following 

 the different degrees of the development of the scale in the same indivi- 

 dual ; the comparative studj' of them, however, has furnished such satis- 

 factory results, that we may hope it will supply the researches indicated. 

 The Corpuscles. — We know that cartilages are provided with corpuscles 

 of different forms, and which are characteristic of that tissue ; a perfectly 

 analogous formation is found in scales. These corpuscles are yellowish, 

 the colour more or less deep, of an oblong form, more or less elliptical. 

 They are seen very distinctly at fig. 13, pi. III. Near the edge of the scale 

 they diminish in size, and at last form only a kind of granulations. Tlie 

 same thing is likewise remarked occasionally round the longitudinal canals. 

 When examined wth a higher magnifying power, their shape can be 

 more distinctly observed ; we perceive that their sides are sometimes a 

 little dilated, that their rounded ends are at other times united to very 

 minute corpuscles, or tenninate irregularly. They become verj'pale, and 

 form large plates in the focus. Their ordinary length is about the hun- 

 dredth part of a millimeter, but, as already mentioned, their size is very 

 variable. These corpuscles appear to be disposed in very regular series, 

 which, however, we have not hitherto succeeded in perceiving distinctly ; 

 they sometimes lie across each other so as to form a kind of cross. They 

 seem to us to perform the same function as the corpuscles of bones and 

 cartilages. Acids render them transparent ; and, according to the ac- 

 count given of the corpuscles of bones, they should contain salts. If we 

 p ace tlic scale, for example, in hyUfOChloric acid and leave it there for 



