CHAPTER VI 



SOURCES, COMPOSITION, AND QUALITIES 



OF IVORY 



What is ivory? We all know it as one of the most attrac- 

 tive art materials, but the structural qualities to which its 

 beauty and appropriateness are due and the sources whence 

 it is derived are often lost sight of by those who fully appre- 

 ciate its rare beauty when they see some artistic object 

 executed in this soft-toned and yet rich and lustrous material. 

 In its most restricted sense, the term "ivory" denotes pri- 

 marily elephant ivory, although as generally employed the 

 designation covers many other forms of dentine. 



The characteristic distinction between true ivory and 

 other forms of dentine appears on examining a transverse 

 section, when wavy lines of different shades are observable, 

 their decussations enclosing minute approximately lozenge- 

 shaped spaces in concentric rows. Under the microscope 

 the tubular structure is revealed, the tubes being exceed- 

 ingly minute and closely set; their smallest branches are 

 immeasurably fine, while at the largest point they only 

 average 1-1000 of an inch. Their angular gyrations are 

 much more marked than are the secondary curvatures of 

 ordinary dentine; these are believed, in both cases, to be 

 due to successive stages of calcification. Through the tubes 

 pass from the central pulp excessively fine threads of a pro- 

 toplasmic substance. The disposition and the peculiar 

 curvature of the ivory tubes serves to render the entire 



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