158 HISTORY OF THE HUMAN BODY 



n , m w v 



vn a ^"p^ 



D 



FIG. 41. Morphology of the visceral skeleton. 



(A) Selachian. (B) Amphibian. (C) Sauropsidan. (D) Mammal. 

 In all the figures the visceral arches are designated by Roman numerals; in the 

 case of the first two the dorsal and ventral segments are further designated by ex- 

 ponent letters (d and v). Other designations are, Ib, labial cartilage; s, spiracular 

 cartilage; o, operculum. In arch VII the arytsenoid and tracheal cartilages are 

 designated by the exponents a and b, respectively. The designations for the stapes 

 represent an interpretation at variance with the one given in the text, but formerly 

 widely accepted. 



