MANDIBULAR ARTERY AORTIC ARCH 101 



This artery he had designated, in his drawings, as an external 

 branch of the afferent mandibular artery, and it was shown 

 lying external both to the nervus mandibularis internus facialis 

 and to the intermandibularis portion of the superficial constrictor 

 of the hyal arch. 



This small and apparently unimportant branch of the so- 

 called afferent mandibular artery of these two fishes might 

 accordingly be the persisting remnant of the primitive man- 

 dibular aortic vessel. I accordingly decided to have these 

 arteries again traced in the adult Chlamydoselachus, and the 

 relations of the arteries to the nerves, ligaments and muscles 

 of the region were now to be carefully determined. This dis- 

 section was confided to my assistant Mr. Jujiro Nomura, and, as 

 the specimen used had to be preserved for other work, the arteries 

 were not injected with ink as they had been in the earlier dis- 

 sections. This makes the dissection much longer and more 

 difficult, but is perhaps not without certain compensating ad- 

 vantages. The veins, unfortunately, could not be satisfactorily 

 traced and are left out of consideration. The arteries, as now 

 found in this one specimen of Chlamydoselachus, are shown in 

 the two accompanying figures, but before describing them brief 

 reference must be made to certain of the earlier descriptions of 

 these vessels. 



Dohrn ('85, '86), as is well known, found two efferent arteries 

 developed in each of the branchial arches of selachian embryos, 

 and those two arteries are said to persist in the adult, one lying 

 posterior to the branchial rays and the other anterior to them. 

 In the hyal arch of these embryos only the posterior efferent 

 artery is developed, the anterior one being represented by 

 lacunae which are said to be distributed along the anterior sur- 

 face of the arch, but not to unite to form a continuous vessel. 

 In the mandibular arch neither posterior nor anterior efferent 

 arteries are developed, the primitive aortic vessel, arising, ven- 

 trally, either directly from the truncus arteriosus or from the 

 ventral end of the afferent artery of the hyal arch, there forming 

 both the afferent and the efferent vessels of the arch A poste- 

 rior efferent artery was, however, considered by Dohrn ('86, p. 



