70 bulletin: museum of comparative zoology. 



(b) Chorda tympani {cd. tym.). This nerve, which draws off all 

 the sensory elements from the hyomandibular ramus (except possibly 

 some which turn back into the sympathetic trunk), passes laterad 

 on the roof of the middle ear chamber to reach the median face of 

 the quadrate bone (Plate 3, fig. 7, qd.). In its course it passes dorsad 

 of the ligament of the columella auris (Plate 3, fig. 7, clml. aur. and 

 Plate 7, fig. 20, lig. tym.) and then follows the quadrate ventrally on 

 the anterior side of the middle ear chamber {aur. m.). It at once 

 enters the cavity of the articulare (Plate 6, fig. 18) through a special 

 foramen. Its course is now cephalad within the jaw; but at some 

 distance forward it passes out through the dorsal side of the articulare 

 (or angulare) to take a position on the dorsal side of Meckel's cartilage, 

 which is here exposed (Plate 5, figs. 14, 15). It keeps this position 

 in its forward course until joined by mandibularis V, which comes down 

 on to it from the dorsal side. It becomes included within the same 

 perineurium with this mandibular ramus, gradually shifting around 

 to the dorso-median side of it (Plate 5, fig. 13). At about the middle 

 of the length of the jaw it is split off with a large somatic-sensory con- 

 tingent and passes out of the foramen as previously (p. 59) described 

 (Plates 2, 3; Plate 5, fig. 12). 



The question of the homology of the chorda tympani in the different 

 vertebrate groups has been recently discussed by Sheldon (:09) in a 

 very thorough manner and it need only be added here that Anolis 

 offers no obstacle to the conclusions there reached. My studies of 

 Anolis embryos in connection with the present work show the chorda 

 tympani to have a history similar to what it has in mammals (Emmel 

 :04), in that it belongs to a posttrematic ramus which is di-awn across 

 the developing tympanum after it has established connections distally 

 with the lower jaw. 



Versluys (:03) has recorded for Lacerta a development similar to 

 that of Anolis and shows in an embryo with one open cleft that the 

 chorda tympani passes posterior to the cleft to reach the lower jaw. 

 He interprets the adult condition as due to the fact that the closing 

 membrane of this cleft does not give rise to the adult tympanum, 

 this structure being developed posterior to the chorda tympani nerve. 

 Thus the latter is a^true posttrematic ramus notwithstanding the evi- 

 dence to the contrary wiiich is presented in the adult. 



In the adult Anolis the chorda tympani can be followed in the main 

 to its terminal branches, and the close correspondence between these 

 and the distribution of taste buds in the lower mouth region adds a 

 new kind of evidence to support the conclusion that the chorda tym- 

 pani is the nerve of taste for the tongue region. 



