286 Dr L. Mandl's Besearches on the 



After what we have advanced, there is no need of repeat- 

 ing how much our opinion is opposed to that of authors, who 

 consider the cellular lines to be the edges of the secreted lay- 

 ers of the scale. 



Our investigations have, therefore, proved, that scales are 

 not to be considered as produced by the secretion of the skin, 

 but that an internal nutrition, a true growth, takes place in 

 these teguinentary appendages. Of this fact the teeth, found 

 in the greater number of scales, furnish the most striking il- 

 lustration, by the successive developments which they under- 

 go : the canals, in their relation to the skin, tend to support 

 this opinion ; the cells (which may be termed granules when 

 they are filled) undergo successive changes, as has been pointed 

 out, and consequently prove that they are subject to augmen- 

 tation and nutrition, and do not owe their origin to a secretion. 



It is farther proved, that it is necessary to make a distinc- 

 tion between the two entirely different layers entering into the 

 structure of the scale ; layers different in their organization, 

 their mode of growth, and the number of parts composing 

 them ; the superior layer, resembling corpuscular cartilages 

 in its structure, presenting corpuscles and lines, diflPers essen- 

 tially from the inferior fibrous layer. But here one point yet 

 remains for ulterior researches to determine. We have stated 

 that the fibrous lamellfE of the under layer, formed one after 

 the other, gradually advance beyond each other, and that 

 on the projecting edge of the most recent lamellae, new cel- 

 lular lines are formed, which thus constitute the continuation 

 of the superior layer. Are these cellular lines formed alto- 

 gether independently of the inferior layer, or are they the^ 

 result of the elevation of the latter, which, however, by such 

 an elevation, would undergo a complete transformation ? This 

 latter opinion is contradicted by the essentially different struc- 

 ture of the two layers ; by the number of the inferior lamel- 

 lae being sometimes much more considerable, at other times, 

 much smaller than that of the lines ; and by the formation 

 of the teeth, which is altogether independent of the infe- 

 rior layer. But we might adduce, in support of this opinion, 

 the transformation, for example, of cartilages into osseous tis- 

 sue, two organizations essentially different ; it may be alleged 

 that a lamella produces numerous cellular lines on its surface. 



