34 BBITISH BIBDS 



notably absent from the passerine birds (the Sparrows, Crows, Books, 

 and small perching birds generally), and from the Hornbills, Toucans, 

 Woodpeckers, and that varied assemblage known as picarian birds. 

 On the other hand, the Storks, Hawks, and most of the larger birds, 

 have the muscle. But among some of these it is absent ; thus, the 

 Owls on the one hand, and the Herons on the other, have no ambiens ; 

 but from their general resemblance in other particulars to birds 

 which have an ambiens, it was thought by Professor Garrod that 

 the loss in them was a recent event, and that they might be fairly 

 placed in one great group of birds with an ambiens which he termed, 

 somewhat lengthily, the ' homalogonatsB,' or normal-kneed birds, 

 reserving the name ' anomalogonatae,' or abnormal-kneed birds, for 

 the passerines, &c., without an ambiens. 



CLASSIFICA TION. 



One great advantage of the study of* birds is that the amount of 

 facts to be learnt in anatomy is far less than with some other 

 groups. They are wonderfully uniform in structure. There is less 

 difference in structure between an ostrich and a humming-bird than 

 between, say, a lizard and a crocodile. Though this may be gratify- 

 ing to the student of birds who is content with a broad knowledge of 

 anatomical fact, it has its disadvantages — very distinct disadvantages 

 — to those who want to arrange and classify the species. As there 

 are computed to be over eleven thousand different kinds of birds, it 

 is clear that an arrangement of some kind is wanted ; we must have 

 an artificial brain in which to store the characters of each bird in 

 their proper place. But before we can consider this it is necessary to 

 consider first what place birds as a whole occupy in Nature. It 

 used to be thought that warm-blooded birds ought to be put near to 

 the warm-blooded mammals. But it is now the general opinion 

 that, as we have before pointed out in relation to certain details of 

 structure, their proper place is in the neighbourhood of the reptiles. 

 In fact they are regarded as a separate division of an order of 

 vertebrated animals which has received the name of Sauropsida, 

 which signifies ' lizard- like ' animals. 



Now, as to these eleven thousand, how are they to be divided ? 

 To this simple question innumerable answers have been given — it 

 is hardly an exaggeration to say as many answers as there are 

 ornithologists. Every part of the body has had its turn in affording a 



