Dr Maudl on the Structure of the Scales of Fishes. 27 



valves. This opinion, first expressed by Leuwenhoek, and 

 adopted without modification by all subsequent authors, rejects 

 therefore entirely the idea of an internal nutrition, or true 

 organisation, which would have exhibited in a scale a tissue 

 receiving and conducting nutritive substances, and undergoing 

 various degrees of development. 



Now, the result of our researches on the structure of scales 

 precisely proves the existence of this organisation, which has 

 escaped the observation of the authors alluded to. If we ask 

 the cause of this, we will readily find it in the insufficiency of 

 the means they employed. No one had made use of a com- 

 pound microscope, nor any considerable magnifying power ; 

 scales were examined ■«dth the aid of a glass, magnifying from 

 five to ten times at the most, and the comparative study of 

 these appendages of the skin in different families, and in the 

 successive degrees of their development, was entu'ely neglected. 



We may therefore say, Avithout hesitation, that we have 

 been the first to employ more effective means of investigation. 

 The magnifying power used in studying the internal structure 

 was always three hundred times ; and it is on this scale that 

 the drawings for the illustrative plate were executed. 



We have by this means proved that the greater part of scales 

 ai'e composed of two layers lying one above the other ; the 

 lower presenting the structure of fibrous cartilages, the upper 

 that of corpuscular cartilages ; the latter, besides, shewing a 

 variety of lines, which we shall prove to originate in the fusion 

 of the primitive cells. These two layers are traversed by 

 longitudinal lines, which belong to both of them. 



We shall treat of each of these pai'ticulars by itself, afford- 

 ing in the first place an idea more in detail, of a scale as it ap- 

 pears under a less magnifying power ; for example, a hundred 

 and fifty times. 



Let us take as a specimen a well developed scale ; tliat of tlic carp for 

 example. (PI. III. Fig. 2). We observe upon it longitudinal lines, tending 

 from a common point towards the circumference, tlic number being not so 

 considerable but that they may easily be counted. The place where these 

 lines converge, or at least to which they arc directed, is of greater or less 

 size ; this we call the focus. IJetwccn the longitudinal lines, and more or 

 less parallel with the margins, a very considerable number of lines may be 

 observed, which are interrupted by the longitudinal lines, and which either 



