286 RAYMOND PEARL 



functional never show manifestations of broodiness. Evidence 

 on this point is found in cases of incomplete hermaphroditism 

 such as that described by Pearl and Curtis (7). In the case 

 referred to, the bird, No. 16D, had a non-functional ovary. 

 Her record shows that she never manifested the slightest signs 

 of broodiness. Still more striking evidence is afforded by the 

 case of bird No. 8051, which was described by Pearl (6). This 

 bird had an ovary which was apparently entirely normal, but 

 remained throughout life in an infantile condition. This bird 

 was hatched on March 29, 1909, and died August 24, 1912. 

 During the whole life she never visited the nest, or showed in any 

 way the slightest manifestations of broodiness. A photograph 

 of the ovary of this bird is given in the paper cited. This is 

 apparently a case of a normal but non-functional ovary and no 

 broodiness occurred. 



Interesting light has recently been thrown on the question of 

 the physiological condition of a brooding bird by the very thor- 

 ough and extensive investigation of Gerhartz (2). This author 

 shows that the state of broodiness is one of profound physio- 

 logical rest or depression. He says: (loc. cit. p. 44). 



" Der Netto-Energieverbrauch fur die auf dem Nest sitzende 

 Bruthenne ist ausserordentlich niedrig: 53.4 Cal. pro Kilogramm 

 Korpergewicht und Tag. In derselben Periode liegt der Energie- 

 verbrauch bei der night sitzenden, aber sich doch sehr ruhig 

 verhaltenden Henne ebenfalls sehr niedrig: bei 74 Cal. Geht man 

 von dem erstgenannten Minimalwert aus, so zeigt sich, dass der 

 Energieverbrauch beim Huhn, das in normaler Ruhe ist und 

 sich in einem geraumigen Kafig aufhalt, im allgemeinen um 

 59.5% des Minimalwertes hoher liegt (Plus von 31.73 Cal. 

 pro Kilogramm und Tag), in der Mauserperiode aber gar der 

 pro Kilogramm und Tag erforderliche Energiebetrag um 84% 

 des Minimal wertes steigt, also fast den doppelten Wert erreicht. 

 In der Legeperiode erhoht sich der Bedarf um fast das Dreifache." 



This discovery that the brooding state is one of physiological 

 depression is somewhat contrary to the common belief of poul- 

 trymen, who have usually supposed that broodiness indicated a 

 condition of unusual physiological excitation. The precise 

 measurements of energy metabolism which Gerhartz has given 

 are, however, conclusive. It is not clear, from the behavior 

 standpoint, what the relation is between the manifestations of 



