128 



A HISTORY OF 



the place of eyes ; the heart beats in the man- 

 ner of every embryo where the blood does not 

 circulate through the lungs. In about four- 

 teen hours after this, the chicken is grown 

 more strong; its head, however, is still bent 

 downwards ; the veins and arteries begin 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 distinctly appear ; and five other vesicles 

 are seen, which soon unite to form the rudi- 

 ments 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 heart, that 

 was hitherto exposed, is now covered up with- 

 in the body, by a very thin transparent mem- 

 brane ; and, at the same time, the umbilical 

 vessels, that unite the animal to the yolk, now 

 appear to come forth from the abdomen. 

 After the fifth and sixth days, the vessels of 

 the brain begin to be covered over; the wings 

 and thighs lengthen ; the belly is closed up, 

 and tumid ; the liver is seen within it, very 

 distinctly, not yet grown red, but of a very 

 dusky white ; both the ventricles of the heart 

 are discerned, as if they were two separate 

 hearts, beating distinctly ; the whole body of 

 the animal is covered over ; and the traces of 

 the incipient feathers are already to be seen. 

 The seventh day, the head appears very large; 

 the brain is covered entirely over ; the bill 

 begins to appear betwixt the eyes ; and the 

 wings, the thighs, and the legs, have acquired 

 their perfect figure.' Hitherto, however, the 

 animal appears as if it had two bodies ; the 

 yolk is joined to it by the umbilical vessels 

 that come from the belly ; and is furnished 

 with its vessels, through which the blood cir- 

 culates, as through the rest of the body of the 

 chicken, making a bulk greater than that of 

 the animal itself. But towards the end of in- 

 cubation, the umbilical vessels shorten the 

 yolk, and with it the intestines are thrust up 

 into the body of the chicken, by the action of 



Halter. 



the muscles of the belly ; and the two bodies 

 are thus formed into one. During this state, 

 all the organs are found to perform their se- 

 cretions ; the bile is ibund to be separated, 

 as in grown animals ; but it is fluid, transpa- 

 rent, and without bitterness : and the chicken 

 then also appears to have lungs. On the tenth, 

 the muscles of the wings appear, and the fea- 

 thers begin to push out. On the eleventh, 

 the heart, which hitherto had appeared di- 

 vided, begins to unite; the arteries which be- 

 long to it join into it, like the fingers into the 

 palm of the hand. All these appearances 

 only come more into view, because the fluids 

 the vessels had hitherto secreted were more 

 transparent; but as the colour of the fluids 

 deepen, their operations and circulations are 

 more distinctly seen. As the animal thus, by 

 the eleventh day completely formed, begins 

 to gather strength, it becomes more uneasy 

 in its situation, and exerts its animal powers 

 with increasing force. For some time before 

 it is able to break the shell in Avhich it is im- 

 prisoned, it is heard to chirrup, receiving a 

 sufficient quantity of air for this purpose, from 

 that cavity which lies between the membrane 

 and the shell, and which must contain air to 

 resist the external pressure. At length, upon 

 the twentieth day, in some birds sooner, and 

 later in others, the inclosed animal breaks the 

 shell within which it has been confined, with 

 its beak ; and, by repeated efforts, at last pro- 

 cures its enlargement. 



From this little history we perceive, that 

 those parts which are most conducive to life, 

 are the first that are begun : the head, and 

 the back-bone, which no doubt inclose the 

 brain, and the spinal marrow, though both 

 are too limpid to be discerned, are the first 

 that are seen to exist: the beating of the 

 heart is perceived soon after : the less noble 

 parts seem to spring from these ; the wings, 

 the thighs, the feet, and, lastly, the bill. 

 Whatever, therefore, the animal has double, 

 or whatever it can live without the use of, 

 these are latest in production : Nature first 

 sedulously applying to the formation of the 

 nobler organs, without which life would be of 

 short continuance, and would be begun in vain. 



The resemblance between the beginning 

 animal in the egg, and the embryo in the womb, 

 is very striking ; and this similitude has in- 



