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DR SUTHERLAND SIMPSON ON 



On May 2nd, 1908, in Musselburgh, Scotland, I secured two hens (Dorkings) of the 

 same brood, two years old. The one (A) was " broody" ; the other (B), which I meant 

 to use as a control, was a laying hen. They were kept in the same room with plenty 

 of air-space, good light and ventilation, and under similar conditions with regard to 

 food and external temperature. A nest made up of old rags and straw containing eight 

 eggs was provided for A in a shallow open box in one corner of the room, on which she 

 at once established herself, and B was allowed to roam about freely in the same room. 

 The rectal temperature of each was recorded daily at 7 a.m., 7 p.m., midnight, and 

 occasionally at more frequent intervals when opportunity permitted. Precautions were 

 taken by gentle handling to avoid inaccurate readings which might possibly result from 

 excitement or struggling, and the clinical thermometer used was inserted three inches 



p.m. Midn't 



Noon. 



p.m. 



42° C. 



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Fig. 1. — Chart showing temperature curves from hens A (interrupted line, brooding) at end of first week of incubation, and B 

 (continuous line, control), May 9th and 10th. Observe that the 24-hour range in A (brooding) is much less than in B 

 (control). The figures at the bottom indicate hours, and at the left side degrees centigrade. 



into the cloaca and rectum and held in position for three minutes. The room tempera- 

 ture was taken at the same time. The readings obtained are shown in Table I. 



From a glance at the figures it will be seen that during the day the temperature of 

 the incubating hen is almost invariably lower than that of the active one, but at mid- 

 night, when the last observation for the day was made, it is usually higher. On four 

 occasions, viz. 9th-10th, 16th-17th, 23rd-24th, and 30th-31st, continuous records 

 were taken at short intervals throughout the twenty-four hours, and in all of these, 

 with the exception of the last, this fact is brought out more clearly, viz. that during 

 the day the rectal temperature of the brooding hen is lower than that of the control, 

 while during the night the reverse is almost always the case. (See figs. 1 and 2.) 



The last twenty-four-hour period came after the chicks were hatched — May 30th- 

 31st, — and here the two curves run fairly parallel, the temperature of the mother hen, 

 however, showing a greater range than that of her companion. (Fig. 2.) 



Between 7 p.m. on the 22nd and 9 a.m. on the 23rd, four chicks were hatched. 

 Subsequent examination of the remaining four eggs showed that one contained a dead 

 chick, almost full time, while the other three were infertile. 



