16 NATURALIST'S CABINET. 



Progress of incubation i?i the natural way. 



greater length than they would have done in 

 their proper place. They have been seen two 

 inches and a half long, and three lines and a 

 h#if in diameter at the base; sometimes they 

 grow curved like ram's horns, and at others like 

 tnose of goios. 



The progress of the incubation of the chicken, 

 in the natural way, is a subject too curious and 

 too interesting to be passed over without notice. 

 The hen has scarcely sat on the eggs twelve 

 hours, when some .lineaments of the head and 

 body of the chicken appear. The heart may be 

 seen to beat at the end of the second day : it has 

 at that time somewhat the form of a horse-shoe, 

 but no blood yet appears. At the end of two 

 days two vesicles or blood are to be distinguish- 

 ed, the pulsation of which is very visible : one 

 of these is the left ventricle, and the other the 

 root of the great artery. At the fiftieth hour, 

 one auricle of the heart appears, resembling a 

 noose folded down upon itself. The beating of 

 the heart is first observed in the auricle, and 

 afterwards in the ventricle. At the end of se- 

 venty hours, the wings Me distinguishable; and 

 on the head two bubbles are seen for the brain, 

 one for the bill, and two others for the fore and 

 hind part of the head. Towards the end of 

 the fourth day, the two auricles, already visible, 

 draw nearer to the heart than before. The liver 

 appears towards the fifth day. At the end of a 

 hundred and thirty-one hours, the first voluntary 



