THE ANATOMY OF A BIRD 81 



walls, the large cavity of which in all probability contained air-sacs. 

 Even some of the jumping Dinosaurs, to which reference has already 

 been made, seem to have possibly had lungs constructed on the 

 bird type. We see, therefore, that even where a bird is, so to speak, 

 most characteristically a bird in the subsidiary mechanisms of 

 flight it betrays a likeness to the comparatively grovelling reptile, 

 letting alone the aerial and more bird-like Pterodactyles. 



Brain. 



The brain of birds is large in proportion to the body, thus 

 contrasting with that of the unintelligent reptile. From some 

 tables on the matter which have been published, it appears that, if 

 weight of brain goes for anything, the goldfinch is one of the most 

 intelligent of birds. The weight of its brain is one-fourteenth oi 

 the entire weight of the body. The most unintelligent of all is the 

 domestic fowl, whose body is 412 times heavier than its brain. The 

 size of brain, however, seems to be largely a matter of the size of 

 the bird : generally speaking, the smaller birds have heavier brains, 

 and vice versa. One might have expected something from the 

 apparently intelligent Parrot ; but the brain of the ' Amazon ' is only 

 one forty-second part of the weight of its body. Even the cruel and 

 bloodthirsty Hawk, which one associates with brutality and ignor- 

 ance, has a brain which is but little heavier. 



The front part of the organ, known as the cerebral hemispheres, 

 or, more briefly, as the cerebrum, is that part of the brain which 

 is associated with intelligence. Now among the mammals this 

 part of the brain is generally much furrowed, the brain surface being, 

 therefore, increased without any actual increase in the skull-spaco 

 required. This furrowing is met with in most mammals, but not 

 always in the smaller and in the less intelligent kinds. But hi 

 the bird's brain there are no convolutions : the surface is as smooth 

 as in the reptile. Not even in the artful Raven, which some hold 

 as the most highly developed of birds, is there a trace of the fur- 

 rowing which one rightly associates, so far as the mammalia are 

 concerned, with a high position in the series. The hinder part of 

 the brain i? known as the cerebellum ; between this and the 

 cerebrum are the optic lobes, of which there are only two, the 

 mammals having four. From the brain arises the spinal cord, or 

 marrow, which runs in the canal formed by the vertebrae, just as 



