122 DR DAVY ON THE TEMPERATURE OF THE COMMON FOWL. 



On the principal results, as given in the summary, I shall comment but little. 

 Some of them, especially the near equality of the temperature of the sexes before 

 maturity, and the lowering of the temperature of the female at the period of 

 laying, may be viewed as physiological problems ; others, as the loss of weight 

 during incubation, with a fall of temperature, and the contrary as to temperature 

 during the period of moulting, seem in harmony with what might be expected 

 according to the theory of animal heat. In the one case, there being a loss of 

 substance of the individual in connection with diminished nutriment, without 

 apparently a febrile disturbance of health; whilst in the other case, it would seem 

 there was such a disturbance, with an elevation of temperature, such as is 

 witnessed in febrile diseases. 



The change of temperature that takes place in the chick on quitting the egg is 

 remarkable, and, as it appears to me, strongly in support of that view of animal 

 heat, in which respiration and the formation of carbonic acid by the union of 

 oxygen with carbon, is considered its principal source. In the egg, just before 

 hatching, the chick is of a temperature rarely exceeding 100°, and that derived 

 more from the incubating mother than from the organic changes in progress ; 

 but no sooner is the hatching completed, and the young bird freely respires : 

 than there is a sudden elevation of temperature. In one instance, in which I 

 had an opportunity of watching a gosling in the hatching act, the temperature 

 actually rose, and that suddenly, from about 100" to 100", after the manner of a 

 hybernating animal, such as the dormouse, in which in passing from its torpid to 

 a state of activity without taking food, there has been, as I have noticed, a rise of 

 temperature from 56° to 99° 5.* 



It is also remarkable how soon the young fowl, after becoming tolerably 

 fledged and capable of securing adequate food, which would seem to be simul- 

 taneous with the consumption of the internal provisional yolk, its earliest 

 nourishment, it attains a comparatively high temperature. Thus of 11 — 7 

 of them thirty-one days old, 4 thirty-five — the average temperature in the 

 middle of October was 108 o, 73; the lowest in any one instance 108°, the 

 highest 109*5 : and I have found the temperature of nestlings also comparatively 

 high, — a young swallow, fully fledged, just after being taken from the nest on 

 the 28th July, was 108°. 



Dr William Edwards, in his very interesting work, " On the Influence of the 

 Physical Agents on Life," has come to the conclusion that " the power of pro- 

 ducing heat in warm-blooded animals is at its maximum at birth, and increases 

 successively until adult age," — a conclusion which seems to me questionable, and 

 requiring, if admitted at all, to be received with many restrictions. Some of the 

 results I have obtained are opposed to it, and others might be mentioned tending 

 to invalidate it. 



* See Physiological Researches (1863), p. 85. 



