180 COMPARATIVE ANATOMY. 



tube along a canal in the upper jaw, opening on the lateral surface of the head 

 near the snout. This prolongation consists of two fibrous tubes, one lying 

 within the other (Fig. 149, IS, AS). 1 



A longitudinal muscle, acting as a retractor (Fig. 1-19, Re, Re 1 ), extends 

 inside the organ along its whole length, and is inserted into a papilla (.Pa) lying 

 in the aperture on the side of the head. 



A large gland (orbital gland) 2 (D) is grouped around this muscle within 

 the broad vesicular portion of the organ, and empties its secretion into the 

 lumen of the tube-like portion (Fig. 149, a, b, c). The duct of a second large 

 gland (tentacular gland) which is embedded within the maxillary cavity 

 (Fig. 149, TD), perforates the lateral wall of the maxilla, and opens into the 

 tube-shaped section of the organ, near its distal end, close to the above- 

 mentioned papilla. 



The physiological function of this apparatus, which occurs quite isolated 

 in the Animal Kingdom, cannot at present be explained with certainty. It 

 probably acts as a spouting apparatus, and (if the secretion of the glands be 

 poisonous) as a weapon of offence ; and thus, together with the remarkably 

 developed olfactory organ, it would serve in some measure to make up for the 

 non-functional, or partly non-functional eyes and auditory organ. It is 

 improbable that it serves as a " tentacle," or organ of touch, as was formerly 

 supposed, as the necessary nerves and sensory epithelium are not known to 

 be present. 



BIBLIOGRAPHY. 



BLAUE, J. Untersuch. ub. d. Bau dcr Nasenschleimhaiit bai Fischcnund Amphibicn, 



namentl. ub. Endknospcn als Endapparatedes Nerv. ol/actorius. Arch.f. Anal, 



u. Physiol. 1884. 

 BORN, G. Numerous Papers on the structure of the nasal cavity of Amphibia, and 



on the naso-lacrymal duct of all the chief Vertebrate groups, in the Morphol. 



Jahrb. Bd. II., V., VIII. 

 GEGENBAUR, C. Ueber die Nasenmuscheln der Voyel. Jen. Zeitschr. Bd. VII. 



1873. Ueber das Rudiment einer septalen Nasendriisc beim Menschen. Morphol. 



Jahrb. Bd. XI. Heft 3, 1885. 

 KANGRO, C. Ueber Entwick. u. Bau der Steno'schen Nasendruse der Saugethicrc. 



Inaug. Dissert. Dorpat, 1884. 

 KLEIN, E. Contributions to the Minute Anatomy of the Nasal Mucous Membrane, 



and of Jacobson's Organ in the Guinea-pig. Quart. Journ. Micros. Science, 



Vol. XXI. 1881. 

 KOLLIKER, A. Ueber die JaJcobson'schen Organe des Menschen. Grat.-Schrift der 



Wiirzburger med. Facultdt fur Einecker, 1877. Zur Entwickl. d. Auges und 



Geruchsorganes menschl. Embryonen. Grat.-Schrift fur die Ziiricher Uni- 



versitat, 1883. 



LEYDIG, F. Die in Deutschland lebenden Artcn der Saurier. Tubingen, 1872. 

 SCHWALBE, G. Ueber die Nasenmuscheln der Sdugethiere und des Menschen. Sitz.- 



Ber. der physic. -cecon. Gesellsch. zu Kdnigsberg, XXIII. 1882. Lehrb. der 



Anatomie der Sinnesorgane. Erlangen, 1883. 

 WIEDERSHEIM, R. Das Kopfskelet der Urodelen. Morphol. Jahrb. Bd. III. 1877. 



Die Anatomie der Gymnophionen. Jena, 1879. 



1 In the embryo the ' ' tentacle " appears to be wanting, but the eye is more distinct 

 than later. 



2 This probably corresponds to a metamorphosed Harderian gland. 



