Temperature of Birds 3 



to a less extent, were also affected by the leaping motion, resulting in the reduc- 

 tion of the toes to four, and the lengthening, and approximation of the meta- 

 tarsals 2-4 to form a 'cannon' bone. 



"The body clothing at this time was probably scale-like, the scales being of 

 relatively large size and probably having a median ridge, or keel, recalling the 

 keeled scales of many living reptiles. Those covering the incipient wing, grow- 

 ing longer, would still retain their overlapping arrangement, and hence those 

 along the hinder border of the wing would, in their arrangement, simulate in 

 appearance and function the quill feathers of their later descendants. As by 

 selection their length increased, so also they probably became fimbriated, and 

 more and more efficient in carrying the body through space." 



Temperature. It is a generally recognized fact that the temperature of 

 birds is normally very high, but, strange enough, exact data on the subject are 

 not extensive. Recently Mr. A. Southerland undertook to ascertain the tempera- 

 ture of certain " Ratite " birds, and one of the most interesting incidental facts 

 brought out is the demonstration of a progressive increase from the lower to the 

 higher birds ; that is, the forms of birds that are regarded as the lowest in the scale 

 exhibit the lowest normal temperature, while between these and the more active 

 and highly organized there is almost every gradation. This condition also pre- 

 vails at least to some extent among mammals. The Apteryx or Wingless Birds 

 of New Zealand exhibit the lowest temperature thus far recorded among birds, 

 the average of three individuals belonging to two species being 37. 9 C. (100.2 F.). 

 Next to the Apteryx come the Emeus, Cassowaries, and Penguins, with an average 

 normal temperature of 39 C. (102.2 F.), while theTinamous examined showed 

 a range from 39.2 C. to 41.3 C., or an average of 40.6 C. (105 F.), "which 

 brings them up to the lower limit of the range of temperature usual for ducks, 

 gp u me birds," etc. The common fowls when lifted quietly off their perches at 

 night have a temperature of 40.6 C. (105 F.), but when lifted by day from 

 nests whereon they are brooding, their temperature averages 41. 7 C. (107 F.). 

 From these birds there is another decided advance when we come to the great 

 groups of small and excessively active birds such as Sparrows, Warblers, etc., 

 their temperature ranging from 42 C. (107.6 F.) to 44 C. (111.2 F.), with an 

 average of perhaps 109 F., or fully ten degrees above that of man. 



Feathers. We may now advert to a consideration of the peculiar outer 

 covering of birds; namely, the feathers. A normal feather (Fig. i) consists of 

 a hollow transparent basal portion called the barrel, or calamus, continuous with 

 which is the main shaft, or rachis, which is opaque, roughly quadrangular in 

 cross-section, and filled with a pithy substance. The rachis is furrowed along its 

 inner surface ; that is, on the side next the body of the bird. From the rachis 

 above the barrel arise a " series of lateral branches, the barbs or rami, which in 

 turn give rise to the barbules, and these to minute, often hooked processes, the 

 barbicels" (Fig. 2). It is by the hooking together of these processes that the 

 web is produced and strength is given it to resist or act upon the air. Springing 

 from the under side of the feather, in many cases, at the juncture of the barrel 

 with the web-bearing portion, is a secondary feather, or aftershaft, as it is called. 



