(53) A. V. Haller (Sur i a formation du coeur dans le 

 poulet, 1758) observed within 70 hours of age, a sac that 

 was not the rudiment of the beak and nothing more than the 

 forehead (bullam dicit auctor, quae nihil aliud est, quam 

 frons) . 



Wolff in the dissertation "Theoria generationis" 

 distinctly distinguished both these parts after five days 

 of incubation. 



Malpighi ("De formations pulli in ovo", 1867) also 

 considered this formation as the forehead. In Fig. 20 of 

 his work, relative to which Tredern stated that it was less 

 thoroughly performed, than many others, the first appearance 

 of the beak was shown on the 7th day of incubation (222) . 



(54) .. Koiter (De ovorum gallinaceorum primo exordio 

 progressusque et pulli gallinacei creationis ordine, 1572) 

 said that he found something similar to the beak after six 



days. 



J. Vesling (Syntagma anatomicum, 1666) confirmed, that 

 the formation of the beak begins after the 8th day. 

 N. Stenon (Observationes anatomicae, 1662) indicated 

 nearly the same period (222) . 



(55) Maitre-Jean (Observations sur la formation du 

 poulet ou les divers changements qui arrivent a l'oeuf a 

 mesure qu'il est couve son exactement expliques etc., 1772) 

 said, that at about the 164th hour of incubation, he found 

 still a soft beak. Tredern later on noticed that the 

 description of the beak development by this author was not 

 accurate and incomplete (auctor de rostro nee accurate nee 

 plane loquitur) (222) . 



(56) Haller confirmed that the hard beak was present 

 after 214 hours of incubation. According to Malpighi the 

 cartilagenous beak existed on the 10th day. Tredern assumed, 

 that a very early period was indicated here (222) . 



(57) This white point on the apex of the beak was 

 also seen by Stenon on the 10th day of incubation (223) . 



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