MOUTH AND NOSE 



but their pull must be very unequal. Some must pull more strongly than 

 others, or act obliquely, and there would result a bulging stimulus at 

 some points which, throughout the ages, might well have resulted in 

 the formation of the diverticula as we now encounter them. It hence 

 seems likely that they are now a part of the opening mechanism of 

 the nose. 



The external aspect of the blowhole of, say, Tursiops, is crescentric 

 and somewhat greater than the half of a circle, the concavity facing 

 forward. Its outer margin is firm, elastic and of rubbery texture. 

 Within this curve is a sort of valve that is much softer to the touch, 

 intrinsically muscular and mobile, which is really a part of the deeper, 

 soft, valvular plug, so that in the living animal while the blowhole 

 is closed one or another part of its surface may move or "work" slightly. 

 The "hinge" of this valve stretches transversely between the points 

 of the arc, and when expiration is desired the posterior part is merely 

 withdrawn within the spiracle and sinks into the highly elastic tissue 

 anterior to the nostril. 



As far as concerns surface indications of muscular action during respir- 

 ation, all we can tell is that the nasal valve is opened by contraction 

 of certain of the rostral muscules, and that in closure there is tension 

 from laterad of the blowhole, but whether the latter is voluntary or in- 

 voluntary is not clear. Of course there is intricate action and interaction 

 of the deeper nasal musculature, but discussion of this I shall leave in 

 the capable hands of Ernst Huber. 



There still remains for discussion the astonishing nasal passages of 

 the Kogidae and Physeteridae or sperm whales, reported on by Pouchet 

 and Beauregard (1885), Le Danois (1910), and Kernan and Schulte 

 (1918) . The conditions are so excessively involved, however, that writ- 

 ten descriptions can hardly be clear without extensive diagrams, which 

 so far have not been published. For a proper understanding of these I 

 am indebted to H. C. Raven, who has most generously placed at my 

 disposal a description and diagrams of the head of a young cachalot 

 which he recently dissected. He will himself report upon this in detail 

 so it is wished here to describe briefly only such points as are necessary 

 for a general discussion. In the cachalot, then, the left nasal aperture of 

 the skull is huge and the right relatively minute. From the skull the 

 lumen of the left passage extends for many feet along the left side of 

 the spermaceti organ, opening upon the left side of the antero-superior 

 part of the snout in a somewhat S-shaped orifice. The right nostril 

 leaves its small cranial orifice and expands laterally to extraordinary 



[99] 



