CETACEA. 137 



their capacious jaws, and also the eyes, being beneath ; 

 hence, in order to admit of uninterrupted respiration, 

 the situation and structure of the nostrils are modified 

 accordingly. 



These animals are called blowing Cetacea, because, 

 in consequence of the structure of the nostrils, they 

 are capable of throwing up jets of water or spray accom- 

 panied with a loud noise ; this act is termed blowing, 

 and the nasal orifices blow-holes or spiracles ; they open 

 on the top of the head, and lead to two large membra- 

 nous pouches seated immediately below the integument. 

 These pouches are receptacles for fluid, which, being 

 forced up into them, is prevented from returning into 

 the throat by certain valves furnished with strong muscles, 

 lodged above the intermaxillary bones (see Fig. 91, 



'-i vlVTuAXycvjE^Bwrea^ 





91.— Skull of Dolphin. 



the skull of the Dolphin) ; it is in the hollow at the top 

 of the head that these pouches are placed. The poste- 

 rior nasal passage is furnished with longitudinal and cir- 

 cular muscular fibres, and opens into the j)harynx, or 

 back part of the mouth ; and into it the larynx rises in 

 the form of a pyramid, and the circular fibres of the nasal 

 passage have the power of grasping it by their contrac- 

 tions. The channel, therefore, from the larynx thorugh 

 the posterior nasal passage into the pouches is plain. 

 Now these pouches are lodged, as we have said, beneath 



