712 MR FRANK J. COLE 



19. M. longitudinalis linguse. (Figs. 2, 3, 6, I. I. (Part I.), I. Ig.) 



J. Muller, Innere Ldngenmuskel der Zunge (p. 256). 

 Ayers and Jackson, M. retractor mandibuli (p. 204). 



This may also be regarded as a paired muscle. Posteriorly it projects behind the 

 truncated extremity of the copulo-copularis, and thus far is visible without dissection, 

 but the greater part of the belly is concealed in the cavity of the latter muscle. When 

 its tendon leaves this cavity in front it traverses the channel of the posterior segment of 

 the basal plate, which is roofed over and converted into a tube by tough fibrous tissue, 

 but in front of this again the tendon works only in a groove open dorsally, the floor of 

 which is formed by the two anterior segments of the basal plate and the sides by the 

 paired rails described on p. 773 of my first Part. This groove gradually dies away in 

 front, and is lost a short distance behind the anterior margin of the anterior segment 

 of the basal plate. It serves as a guide to the dental skeleton when the latter is in the 

 mouth, and transmits the tendon of the present muscle when the " tongue " is everted. 



By making a median dorsal longitudinal incision through the copulo-copularis and 

 the roof of the channel of the posterior segment of the basal plate, the longitudinalis 

 linguae, together with the attached perpendicularis, may be removed intact, along with 

 the dental apparatus, and examined carefully under a dissecting microscope. It is then 

 seen to arise as follows : — (a) the dorso-external fibres arise from the lateral under-surface 

 and lateral margin of the superior chondroidal bar, i.e. from practically the whole ventral- 

 surface of this cartilage not occupied by the perpendicularis. It also arises, according 

 to P. Furbringer, from the stout fascia in which this cartilage lies ( = broadened out 

 dorsal linea of the copulo-copularis), but I cannot confirm this either from dissections 

 or sections ; (b) the lateral and ventral fibres, comprising the greater part of the muscle, 

 arise, like a bipinnate muscle, from a median vertical ligamentous (or pseudo-cartilaginous 

 — cp. especially p. 780 of my first Part) partition situated in the longitudinal plane at 

 the posterior end of the muscle ; (c) a small posterior bundle, forming the most ventral 

 fibres of the muscle, arises from the dorsal surface of the posterior tip of the inferior 

 chondroidal bar. (Cp. figs. 2 and 3. On p. 779 of my first Part it is erroneously 

 stated that the longitudinalis linguse has no connection with the inferior chondroidal 

 bar.) The above very curious reinforcement (c), which seems so small and useless, is 

 paired, each half of the muscle receiving a bundle. In the sections the left bundle was 

 much larger than the right. The latter first of all sharply dips down in the median 

 plane between the fibres of the perpendicularis to reach the inferior bar, and the left 

 one does the same immediately behind it. All the fibres of these two bundles, however, 

 do not arise from the bar, but some of them from the vertical sheet described ahove. 



From their origin the fibres of the longitudinalis linguae pass outwards and forwards 

 in a curve in order to embrace the lateral surfaces of the perpendicularis. They soon 

 pass straight forwards (apart from their convergence), and in front of the perpendicularis 

 the muscles of the two sides are closely opposed by their median flat surfaces, but do 



