90 NATURAL HISTORY. 



described next to one another, or placed side by side in collections, by many of those who are in the 

 habit of employing a systematic method of arranging the different genera, would show that such 

 ornithologists consider the relationship between the Swallow and the Swift to be more intimate than 

 that between either of these birds and the Sparrow, Crow, Starling, Lark, &c. But all these last-named 

 birds are what are known as Passerine ; in other words, they possess certain anatomical peculiarities 

 in their organisation, found in them all, and in no other group of birds. If, therefore, the Swift and 

 the Swallow are more nearly related to one another than either is to any other passerine bird, then, as 

 the Swallow is more certainly passerine, the Swift must be so also. But certain naturalists assert that 

 the Swift is not a passerine bird at all, and, if they are correct, it is evident that the Swallow and 

 it cannot have anything to do with one another. Upon this assumption, therefore, the passerine 

 Swallow is much more closelv related to the Sparrow, the Crow, and the Lark, than it is to the 

 Swift, 



" The question, then presents itself -Is it really the case that the importance of the deep-seated 

 anatomical resemblances between the Swallow and the Sparrow, and of the differences between the 

 Swallow and the Swift, is sufficient to justify us, notwithstanding the external similarity between the 

 last-named birds, in believing that the first-mentioned are truly more intimately related the one to the 

 other ] 



" It may be worth while taking a rapid glance at what some of these important anatomical 

 resemblances and differences happen to be one of them is the manner in which the feathers are 

 arranged on the skin. Most of us know that, unlike the hair upon a cat or other quadruped, the feathers 

 of a bird are not uniformly distributed over the surface of the body, but grow in linear clusters called 

 tracts, with naked intervals, termed spaces, between them. This 

 may be readily verified by plucking, say, a Sparrow, and noticing 

 the thick and opaque light-coloured bands formed by the thicken- 

 ing of the skin surrounding the holes, out of which the feathers 

 have been extracted. Between these tracts the skin is seen to be 

 thin and translucent, forming naked spaces through which the 

 colour of the underlying muscles is apparent. 



"The careful study, some five and forty years ago, by the 

 eminent German ornithologist, C. A. Nitsch, led him to the con- 

 clusion, among others, that these feather-tracts are arranged upon 

 a very different plan in the Swallows to what they are in 

 the Swifts, whilst in the Sparrows and their allies they very STERNUM OF SWALLOW (A) AND OF 

 closely resemble the Swallows. Further, he showed that in this SWIFT (B). 



feature the Swifts and the Humming-birds are almost identical. 



Again, the breast-bone, or sternum, in birds is much expanded to give origin to the powerful 

 nuiscles of flight. In both the Swallow and the Sparrow, as in passerine birds generally, its 

 usually oblong figure is modified by the presence of two deep notches, one on each side of the 

 keel, in the posterior margin. But in the Swift there are no such notches to be found, the 

 posterior margin being entire, and in other respects it differs from the same bone in the Passeres, 

 whilst in all it resembles the Humming-bird. In the Sparrow and the Swallow, again, as 

 in the great majority of the passerine birds, there is, at the lower end of the trachea, or windpipe, 

 where the bronchi which place it in communication with the lungs arise, an elaborate special mechan- 

 ism, which is known as the muscular organ of voice or lower larynx, by which they have the power 

 although they do not at all employ it of modulating their note, so as to produce a song ; this is not 

 found in the Swifts. In man, the greater part of the alimentary canal is composed of a tube of small 

 diameter the small intestine which is continued onwards as a more capacious one, the large intestine. 

 These two are not simple continuations one of the other, but the former enters the latter obliquely, the 

 nearer end of the large intestine remaining free as the ' blind gut,' or csecum. In the Swallow and 

 Sparrow, as in all the Passeres, instead of there being a single csecum at the place of junction of the 

 two intestines, there are two. These are not found in the Swifts nor in the Humming-birds. 



" In the Swallow, the Sparrow, and all their true allies, it is always the case that the tendons 

 which contract up the last joints of the toes, are so arranged that the birds have the power of folding 



