THE BODY TEMPERATURE OF THE DOMESTIC FOWL (GALLUS GALLUS). 613 



and artificial incubation of the eggs of the common fowl, and amongst others, the 

 temperature of the fowl and of the eggs during incubation. In one set of experiments, 

 in order to avoid disturbing the hen in determining its temperature, special self- register- 

 ing thermometers were fastened to blocks so cut that their upper surfaces in contact 

 with the hen's body were egg-shaped, the lower surfaces being broad and flat so that 

 they could not be overturned. One of these was placed in each of four nests and 

 left for two or three hours when the reading was made. A second set of readings was 

 obtained from another group of four hens by gently removing the hen from the nest and 

 placing the thermometer in the groin for five minutes. It is not stated at what hour of 

 the day the temperatures were taken, nor whether they were taken at the same hour on 

 successive days. This is a point of considerable importance. In both sets the tem- 

 perature was found to be lowest the first day, and lower on the first three or four days 

 than on the subsequent days of incubation. 



One of Eycleshymer's objects being to find the temperature of the egg on successive 

 days of incubation, this was carefully recorded by a special method, the temperature of the 

 hen being taken at the same time. For the purpose of comparing his results with mine 

 I show the figures he obtained for two series of observations. (Compare Tables IV. 

 and V.) In the first (I.) the temperature of the hen was taken by the self- registering 

 thermometer described above ; in the second (II.) by a clinical thermometer placed in the 

 groin ; in both, the temperature record being that of the under surface of the body 

 which came into direct contact with the eggs. 



The surface temperature of the hen would therefore appear to rise slowly till about 

 the end of the first week, and after that to remain more or less constant ; the tempera- 

 ture of the egg, on the other hand, increases steadily to the end of incubation. 

 According to my observations, which agree with those made in Professor Kice's 

 department, the internal temperature of the incubating hen remains about the same 

 level from the first day until the beginning of hatching, when there is a slight rise, which 

 is probably to be accounted for by the increased excitement of the hen at that time. 

 Eycleshymer's figures are from a single observation daily — he does not say at what 

 hour ; mine show the mean of three daily observations made at corresponding hours on 

 successive days. 



The fact that the surface temperature of the hen rises gradually during the first few 

 days of incubation has also been noted by Cyphers (3). He says : "If during the first 

 few days of incubation we place a suitable thermometer beneath the hen in about the 

 same position as the eggs are placed, there will be imparted to it a temperature of about 

 101° F. (3 8 "3° C.) only, although a glass placed in the rectum will register from 109 to 110 

 (42*8° to 43"3 C C). . . . By the end of the first week of incubation the temperature in 

 the rectum will be about 109 ; by the end of the second week it will have fallen to 108 ; 

 and sometimes by the end of the third week to 106 degrees. One hen with a rectum 

 temperature of 106 at the end of incubation was killed the fourth day following, and was 

 found to have a temperature in the region of the heart of 110° F. (43 , 3° C). 



TRANS. ROY. SOC. EDIN., VOL. XLVII. PART III. (NO. 21). 91 



