80 STUDIES IN COMPARATIVE ANATOMV. 



somewhat irregular, and the lower edge is rather nearer to 

 the median plane (especially in its posterior half) than the 

 Tipper. This aliseptal cartilage forms part of the outer wall of 

 the nasal passage, as well as the inner wall of a transversely- 

 contracted channel which leads from the nasal meatus to a 

 large frontal sinus. The muscular fibres attached to the fore 

 edge of the aliseptal cartilage, which are continuous with the 

 lower set of the transverse fibres of the alinasal pouch, when 

 they contract^ draw the cartilage towards the bony or outermost 

 wall of the nasal chamber, and very effectually close the 

 entrance into the air-sinus. The lower border of the cartilage, 

 for somewhat more than the anterior haK of its extent, is con- 

 nected with the wall of the nasal chamber by a strong band of 

 yellow elastic tissue, which forms part of the dividing septum 

 between the proper respiratory passage and the entrance to the 

 frontal air-sinus; it serves to antagonise the muscular fibres 

 which close the valve. The posterior extremity of the cartilage 

 is connected to the lateral wall by a mass of fibrous and mucous 

 tissue, which forms the anterior boundary of the special respira- 

 tory chamber, and separates this from the channel leading to 

 the frontal sinus. The aliethmoidal volutes are disposed in 

 about seven laminae, which gradually diminish in size backwards, 

 and closely resemble the bony framework of the olfactory organ 

 in the horse. Behind this point the nasal passage lies between 

 the hard palate and the spheno-palatine surface. Its vertical 

 extent in our young example is nearly three inches, but the 

 transverse width is extremely small, and hence the nasal pas- 

 sages seen from behind present the appearance of greatly elon- 

 gated vertical slits. (See p. 50.) 



Dr Watson believes that the valve-like aliseptal cartilage is 

 adapted to obstruct the flow of water into the air-sinuses of the 

 skull during its passage along the narial tubes. We are disposed 

 to question the normal passage of water along this highly 

 sensitive tract. Examination of the parts discovers no valve or 

 other provision for preventing water flowing from behind for- 

 wards^ from gaining free entrance into the olfactory recesses. 

 Moreover, the only important receptacle above the stomach is 

 constituted by the pouch adjacent to the alinasal cartilage. We 



^ See the quotation from Dr "Watson's memoir on p. 54. 



