HUMBOLDT ON THE ORGANS OF THE VOICE. 339 



This cartilage, to which I shall give the name of base (socle) has not 



a b c 



a, "Socle" of Pelecanus alcatras. b, ditto of Pelccanus olivaceus. c, ditto Phasianus garrulus. 



hitherto been well described. It has, on its upper surface, a membrane 

 which divides it into two parts, and which proceeds from it at right angles. 

 This membrane is triangular, and resembles the index of a sun-dial. In 

 the living animal, it is generally visible at the centre of the opening of 

 the glottis : it there forms a partition, the presence of which must con- 

 tribute a great deal to modify sounds and render them more acute : it 

 divides, so to speak, into two currents, the air which is driven by the 

 inferior larynx towards the glottis. I was surprised to find that it was 

 wanting in the glottis of the Palamedea bispinosa. This flat cartilage, 

 thus furnished with a triangular membrane, is immediately attached to 

 the rings of the trachea : it may be considered as a half-ring of a 

 singular construction. 



Besides this base, the glottis of birds is supported by four little 

 bones, which are connected, two by two, in the form of compasses, 

 the anterior pair of which is embraced by the posterior. I do not 



a, Larynx of Ardea cocoes opened, b, bonelets or compass bones. 



hesitate to call these bonelets ; for, in tropical birds their substance 

 is too dense for them to be ranked among the cartilages. They are 

 triangular, diminish towards the extremities, and are joined in pairs 

 by condyles. I have carefully copied those of the great heron with 

 black neck and white floating comb, of the river Magdalena, and 

 which constitutes an intermediate species between the Ardea cocoes 



