HISTORY OF 



part of the broad end in which a cavity has been 

 described, and with its yolk seems to adhere to 

 the membrane there. At the end of forty hours 

 the great work of life seems fairly begun, and the 

 animal plainly appears to move ; the back-bone, 

 which is of a whitish colour, thickens ; the head 

 is turned still more on one side ; the first rudi- 

 ments of the eyes begin to appear; the heart 

 beats, and the blood begins already to circulate. 

 The parts, however, as yet are fluid ; but, by de- 

 grees, become more and more tenacious, and 

 harden into a kind of jelly. At the end of two 

 days, the liquor, in which the chicken swims, 

 seems to increase ; the head appears with two 

 little bladders in the place of eyes ; the heart 

 beats in the manner of every embryo where the 

 blood does not circulate through the lungs. In 

 about fourteen hours after this, the chicken is 

 grown more strong; its head, however, is still 

 bent downwards ; the veins and the arteries be- 

 gin to branch, in order to form the brain ; and the 

 spinal marrow is seen stretching along the back- 

 bone. In three days, the whole body of the 

 chicken appears bent; the head, with its two 

 eye-balls, with their different humours, now dis- 

 tinctly appear ; and five other vesicles are seen, 

 which soon unite to form the rudiments of the 

 brain. The outlines also of the thighs and wings 

 begin to be seen, and the body begins to gather 

 flesh. At the end of the fourth day, the vesicles 

 that go to form the brain approach each other ; 

 the wings and thighs appear more solid; the 

 whole body is covered with a jelly-like flesh ; the 



