2^2 H. H. WILDER, 



Here the thyroid i)rocesses lie on the sides of the larynx, and when 

 viewed from the cardiac side, seem to have preserved their typical 

 form better than in Pipa. A tough membrane stretched on the car- 

 diac side between these two processes, seems to replace the bony 

 plate, referred to by Grönberg as the "thyroid cartilage". On the 

 pharyngeal side, however, broadly expanded wings, apparently from 

 the cartilaginous tips of these processes, enter largely into the for- 

 mation of the resonance box and form broad attachments for the ex- 

 trinsic muscles (Figs. 58 and 60). The resonance box is thus iucom- 

 ])lete upon the cardiac side and may be thus easily opened by removing 

 the membrane. Within are found three cartilages (Figs. 60—61); one 

 .1 median, heart-shaped piece, lying more on the i)haryngeal surface, 

 and a pair of irregularly oval pieces lying higher uj). The paired 

 cartilages were interpreted by Henle as the "ary taeuoids" and 

 the unpaired piece, the "cricoid". The disposal of the muscles, how- 

 ever, and especially the insertion of the lateral extrinsic system about 

 the rima glottis, led me to sus])ect the existence of other genuine 

 arytaenoids lying within the ring and at the point of insertion of the 

 extrinsic muscles. These I found (Fig. 61) as a pair of tiny carti- 

 lages, lying in the position suggested and entirely overlooked by 

 Henle. The discovery of these leads me to interpret the three other 

 pieces as isolated elements of the annulus ; the median piece, perhaps, 

 corresponding to the pharyngeal process, and the two lateral, either 

 to the anterior pharyngeal processes or simply to be referred to the 

 lateral elements of the annulus. 



10. Summary of Part L 



1. In young Necturi and Protei there exists a single pair of 

 laryngo-tracheal cartilages, representing the 5'i' pair of epibranchials. 

 These, by the strain exerted upon them by the rapid growth of the 

 surrounding i)arts, become degenerate in places, which results in 

 fenestrations and more or less comi)lete sei)aration into diifereiit 

 pieces. 



2. Of these i)ieces, the most constant is an anterior pair of" 

 triangular cartilages, lying upon the sides of the rima glottis and 

 known as the arytaenoids; the remaining i)ieces lie ui)on the 

 sides of the trachea and may be called the tracheal elements. 



3. This condition becomes peri)etuated in the higher forms, which 

 ccmstantly j)0ssess a pair of arytaenoid cartilages and a variable 



