THE ANATOMY OF A BIRD 25 



same continent and New Guinea. In both of these animals the 

 heart valve in question is a]so largely muscular, and does not 

 entirely encircle the opening from the auricle. These two mammals 

 also, as everyone knows by this time, have the strange habit for a 

 mammal of laying eggs, which is one among some other reasons 

 which once led naturalists to place them in the neighbourhood of 

 birds. The egg-laying, of course, is not distinctive, since reptiles 

 have the same way of bringing forth their young ; and as to the 

 heart valve, it is rather to be explained by the fact that both types 

 of animals are low in the scale of their respective groups, and there- 

 fore both approach a common ancestral form. 



Voice Organ. 



By their voice, too, birds are distinguished from the rest of the 

 animal creation. Though there may be legends of singing serpents 

 and of talking monkeys, a harsh scream or a growl is the only 

 manifestation of the emotions through the voice which exists until 

 w r e arrive at man. Among birds, the possession of a melodious 

 voice is limited to that group which we term the Passeres. Other 

 birds can scream or utter a dull note, while many are mute. So 

 flexible is the voice organ of these creatures that they are the only 

 animals that can imitate human speech. Here, however, it is not 

 only the Passeres which can imitate the essential attribute of man. 

 The Parrots, of course, are always supposed to be the birds which 

 can talk, but this is far from being the truth. The hoarse utter- 

 ances of most Parrots are left far behind in clearness of sound and 

 correctness of imitation by the little Indian Mynah, which may 

 be usually seen at the Zoological Gardens, and heard to speak. But 

 the Parrot cannot sing. These are the only two groups of birds 

 which have so elaborate and flexible an organ of voice. From this 

 it might be inferred that some peculiarities of mechanism would 

 distinguish the organ in question of these birds, and that is what 

 we actually find to be the case. But, oddly enough, it is not only 

 those birds which have a beautiful voice whose voice organs are so 

 elaborate in structure. The harsh croak of the Raven issues from a 

 syrinx which is as delicately fashioned as that which allows of the 

 exquisitely varied tones of the Nightingale, The word ' syrinx ' has 

 been mentioned ; that is the technical term for the voice organ of 

 the bird, which is formed from a part of the windpipe, as in man 



