AS AN INDEX OF AGE. 7 



is found developing. Mandl thought that these canals serve for the transport 

 of nutritive material from the skin towards the centre of nutrition, in other 

 Avords, that they fill the role of true vessels containing nourishment. 



The Cellular lines. Under this term iNIandl discusses the concentric lines 

 or ridges parallel to the contour of the scale. He does not agree with previous 

 authors in regarding these lines as the projections of secreted and super- 

 imposed la3'ers. According to him, these lines owe their origin to special 

 cells which originally form themselves on the superior surface of the scale ; 

 gradually these cells amplify and elongate, and finally come to represent 

 cellular lines. 



Corpuscles. ^Mandl is the first author to describe definite corpuscles in the 

 tissue of scales. He describes those corpuscles as of a yellowish colour, and 

 of an oblong, more or less elliptical form. They diminish in size towards the. 

 edge of the scale, showing there only a granulated appearance similar to that 

 which one notices sometimes in the vicinity of the longitudinal canals. 

 These corpuscles are usually arranged in a very regular way, sometimes 

 crossing one another in such a manner as to form a cross. Under the action 

 of acids they become transparent. 



These corpuscles are contained in a definite tissue which is situated above 

 the inferior surface of the scale. This tissue is an amorphous tissue like that 

 in which the corpuscles of bone are deposited. The tissue constituting the 

 superior layer of scales thus approaches that of cartilage with non-ossified 

 corpuscles. 



Inferior layer of scale. Beneath the layer with corpuscles is found the 

 inferior layer, which is a fibrous layer built up of fibrous lamellae, in which 

 the fibres cross one another at regular angles, but in which the fibres all 

 follow the same direction in the same lamella. This arrangement approaches 

 that of fibrous cartilage. This inferior layer is thickest at the focus (foyer) of 

 the scale, and thinnest at the borders ; it is this which forms the foundation 

 of the longitudinal canals in the vicinity of the border of the scales. 



Mode of scale formation. Mandl endeavours firstly to establish a dis- 

 tinction between the formation of the superior and inferior layers of scales. 

 According to him, the superior layer, composed of cells, corpuscles, and of the 

 fundamental substance which contains them, develops by growth, which takes 

 place at the periphery round the cellular lines. 



The inferior lamellcB increase by the formation of new lamellse beneath the 

 preceding. The elements necessary for the formation of these lamelhe are 

 brought by the longitudinal canals. The old lamelliB being the smallest, this 

 explaijis why the thickness of the scale ought to increase in degree as one 

 approaches the focus (foyer). 



"Si nous voulons appliquer les resultats que nous avons obtenus dans 

 I'etude de la structure intime des ccailles, ii I'explication de la maniere dont 

 elles se forment, nous verrons tout d'abord qu'il importe de bien distinguer la 

 formation de la couche superieure, et celle de la coiiche infurieure. La 

 premiere, composue de cellules et de leurs bases avcc le tissue qui contient les 

 corpuscles, prend son developement par des accroissements qui ont lieu dans 

 la peripheric, autour des lignes cellulaires ; au moyen, de pareits accroisse- 



