58 THURLOW C. NELSON 



The first comprehensive investigation of the nature and 

 function of the crystalline style was made by Poli (1791-95). 

 He describes accurately the appearance of the style and its rela- 

 tions to the rest of the alimentary system. He was the first to 

 note the presence of the gastric shield, which he likened to a 

 cartilaginous three-pointed arrow, 'sagitta tricuspis,' borne on 

 the head of the style. 



Investigating the physical and chemical properties of the 

 style, he found it to be soluble in water and coagulated by boil- 

 ing water and alcohol. He believed that it served in some 

 way to regulate the flow of ' bile' from the biliary crypts. Cuvier 

 (1805) adds nothing new, but admits the conclusions of Poli. 



From this point on investigators are so numerous that it is 

 best to classify them according to the theory which they sup- 

 ported. 



A. An organ of support. From its position in the alimentary 

 tract, Carus, (1818), believed it to be a vestige of a splanchnic 

 skeleton, homologous with the teeth of the sea-urchin. Garner 

 ('41) believed its function was to give rigidity to the foot. 

 DeBlainville ('48) claimed the simultaneous existence of several 

 styles arising in the sinuses of the biliary canals. He had 

 nothing to say regarding their use. 



B. Mechanical functions. Meckel ('29) considered it homol- 

 ogous with the radula of the Cephalophores, and consequently 

 an organ of mastication. Garner ('41) agreed with this in- 

 terpretation, and thought that the points of the gastric shield 

 served to modify the flow of 'bile' as first held by Poli. De- 

 shayes ('48) gives good figures of the gastric shield which he 

 believed to be important in mastication. Clark ('50) thought 

 that the style acted as a pestle to grind up the alimentary 

 matter. 



Huxley ('53) was the first to consider the style an epithelial 

 secretion. He says, regarding the style of Pteroceras, 



The end of the style is opposed by one or two cartilaginous plates 

 (the gastric shield) upon the principal elevation. It seems probable 

 that the style is secreted by the walls of the pyloric caecum, and that 

 it plays the role of a gastric plate to aid in grinding up the alimentary 

 matter, though its transparent and delicate structure seems ill fitted 

 to this purpose. 



