103 ESCHRICHT AND REINHARDT 



thyroid, in connection with the hyoid, only serves as a semitubular sheath around the trachea 

 properly so called, the anterior (su])erior) limits of which must be set down at the beginning of 

 the arytenoid cartilage. At the same time it is the more evident that the cricoid, on the 

 contrary;, may most properly be said to form part of the trachea itself, as it is itself united with 

 the anterior tracheal rings, and as the ligamentous membrane, compensating for its absent ventral 

 moiety, is miited with the one which fills out the place of the wanting pieces of the tracheal rings 

 on the ventral surface. In the Greenland whale foetuses examined by Sandifort the tracheal bag 

 did not extend further backwards than the hindmost extremities of the plate of the thyroid, so 

 that it only became visible in the notch between these on the hindmost margin of the cartilage. 

 But he was very well aware that such could not be the case in a more advanced age of the animal. 

 And, indeed, in the newborn individual it already extends backwards as far as to the division of 

 the trachea into its two bronchi, or as far along the trachea as its cartilaginous rings are com- 

 pensated for by an aponeurotic membrane. 



The air-bag of the Greenland whale has, like that of the whalebone-whales in general, an 

 exceedingly thick covering of muscles. This covering had in a young hump-back {Megaptera), a 

 thickness of two or three inches. But the muscles by which the air-bag is covered have by 

 no means the form of a membrane. They consist entirely of transversely striped muscular fibres, 

 attached to the lateral margin of the ci'icoid cartilage, as well as to the interrupted extremities 

 of the tracheal rings, forming fascicles, of which the inferior (posterior), at least in their external 

 strata, are turned directly upwards (forwards), the superior (anterior) transversely towards a 

 tendon placed in the mesial line of the fleshy mass, the rest obliquely towards this tendon. 

 Prom without the bag seems to be very large, on account of the thickness of this fleshy mass. 

 But its cavity lined with the mucous membrane appears to be comparatively very small, at least 

 in the dead animal. On cutting through the fleshy mass, it is not met with by the knife until 

 about midway between the division of the trachea and the posterior margin of the thyroid 

 cartilage. When the bag becomes distended by the air which is forced into it during the 

 relaxation of the muscles, the relative size of these parts will, no doubt, be completely 

 altered. 



As the larynx of the whalebone-whales in its ventral surface is so very differently formed 

 from that of the toothed-whales, it is also known to be essentially different from the same in its 

 superior (anterior) extremity, at least as far as it is not nearly so completely enclosed by the 

 muscles of the soft palate. This is especially the case with the Greenland whale. The ascending 

 cornua of the arytenoid cartilages are, as usual, placed in close contact with the epiglottis 

 (fig. 3), forming with the latter an elevation ascending towards the palate. But this elevation is 

 comparatively far shorter than that of the toothed-whales, and accordingly the membrane in which 

 its three cartilaginous parts are enveloped is not continued to their very outmost extremities, so 

 that the respiratory canals appear undoubtedly to be less completely closed before than in the 

 toothed-whales. But we know how unsafe it is, both generally and in respect to these organs in 

 particular, to make inferences from parts as they appear in the dead body, as to their appear- 

 ance during the life of the animal, and we must consider any such supposition as that the 

 water may penetrate from the cavity of the mouth into the respiratory canals, and particularly 

 into the tracheal bag on the larynx, and be again expelled firom thence through the nostrils, to 

 -be quite improbable. 



Before we leave the examination of the larvnx we must still add some observations relative 



