when investigating this subject. It has been determined 

 that a hen's temperature varies slightly with the season, 

 highest in the summer, and nearly, or exactl}^, identical in 

 Mav and October. I am inclined to believe that there is a 

 tendency to an increase of temperature during the mating 

 season, since I have found the cock ring-neck pheasant's 

 temperature much higher than the female's at this time of 

 the bird's physiological year, and Pickrill (141) says that 

 there is an increase of about 2° F. at such times with both 

 sexes of the ostrich. Ingestion of food and muscular activ- 

 ity elevates (slightly) the temperature in man (156) and 

 seems to do so also in birds. The support to this latter 

 statement is indirect only. A setting hen's temperature 

 (166) is lower than that of an active "control" hen, and the 

 "control's" temperature is lower at night, as shown if taken 

 when the bird is gently lifted at night from the perch. An 

 under- fed or a starved hen (165) has a lower temperature 

 than the normal control bird ; this difference borders closely, 

 however, on the domain of pathology, into which it is in- 

 expedient here to enter. 



Birds have bodily temperatures which are only slightly 

 affected (156) by climate. Individuals of the same species 

 in the Arctic region have the same temperature as those 

 in temperate zones, showing the wonderful control of body 

 temperature by the heat centre of the central nervous sys- 

 tem, and nothing shows more vividly the power of this con- 

 trol than the experimental demonstration that a sparrow, 

 with its feathers all clipped oft', maintains its body heat, 

 under ordinary temperatures, quite easily at normal. 



The age of a bird has no relation to its body tempera- 

 ture, except that altrical birds do not acquire a stable and 

 normal temperature curve until ready to leave the nest, or 

 at least until muscular co-ordination is nearly or quite per- 

 fected. Precocious birds seem to have a perfectly function- 

 ating temperature controlling centre at hatching, while con- 

 cerning the age and tem])erature, it may also be said that 

 ducks varying in age from four to twenty-four months 

 exhibited temperatures identical with those of older birds 

 (165). The rectal temperature of a hen, taken immediately 

 after it has laid an ^gg, is said to be 2° F. higher than nor- 

 mal (164). I am unable to say that all these peculiarities 

 of a hen's temperature apply also to all other birds, but until 

 shown otherwise, it is necessary to hold that they do. The 

 normal temperature of man is assumed to be the average 

 of the highest reading of the twenty-four hours, utilizing 

 as large a series of observations as possible, and all of normal 

 adults. Comparative physiology demands the same stand- 

 ard in other homoiothermic animals, having, of course, due 

 regard for individual peculiarities (i. e., nocturnal animals 



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