670 'Or. HARRIS II WILDER, 



of the dorso-trachealis, upon the side of the trachea, directly beneath 

 the insertion of the last-named muscle. 



It is innerved by a recurrent nerve which l)ranches from one of 

 the vagus twigs supplying the external gills. 



4) Depressor laryngis (fig. 7 dl.). 



This muscle arises from the connective tissue upon the ventral 

 surface of the trachea along a diagonal line of origin which runs from 

 the lowest point of origin, upwards and outwards. Its fibres are in- 

 serted into the connective tissue of the larynx between the two constric- 

 tores laryngis. 



A long and very fine nerve issues from the 2"'' branch of the Ramus 

 recurrens vagi, runs transversely across the dorso-trachealis, and supplies 

 the muscle in question. A very fine fibre continues upward and supplies 

 the constrictor laryngis. According to Fischer, this latter twig gives 

 branches to the upper part of the dorso-laryngeus. 



This seems hardly i)robable, not only because, after a most careful 

 search, I have failed to find the branches in question, but also because 

 the muscle receives a sufficient supply directly from the main stem 

 of the Ramus recurrens and considerably lower down. 



5) C o n s t r i c t o r e s et D i 1 a t a t o r e s a d i t u s laryngis 

 (fig. 7 c. a. ?., also woodcuts p. 680). 



These two muscles form a cylindrical band around the entire 

 larynx. This band is divided by four tendinous raphes into four 

 quarters, of which the two ventral ones (external in preparation) form 

 the constrictor es and the two dorsal (towards the oesophagus) 

 the dilatatores. At the superior border of this muscular band, 

 the arytenoid cartilages are small, and enclosed by the four muscles 

 which with their fibres form a complete circle, interrupted only by 

 the raphes. Farther down, however, the cartilage sends out its broad 

 lateral process, which usurps the place of the two lateral raphes, this 

 being the relation of the parts throughout the greater portion of their 

 extent. 



a) C o n s t r i c t o r e s. These , the ventral pair , arise from the 

 median raphe between them, and are inserted mainly into the ventral 

 surface of the lateral process of the arytenoid cartilage, but also by 

 their superior fibres and a few exterior fibres, into the lateral raphe 

 between them and the dilatatores. These small muscles are supplied 

 by a very fine terminal branch of the Ramus recurrens. 



b) Dilatatores, muse, ii o v. Although these muscles form no 



