ANLMALS. 291 



gans ai'e found to perform their secretions ; the bile is found to 

 '^e separated as in grown animals ; but it is fluid, transparent, 

 \ id without bitterness : and the chicken then also appears to 

 ' ■xve lungs. On the tenth the muscles of the wings appear, and 

 ■ le feathers begin to push out. On the eleventh, the heart, 

 hich hitherto had appeared divided, begins to unite ; the ar- 



I Ties which belong to it join into it, like the fingers into the 

 •Jm of the hand. All these appearances only come more into 



■lew, because the fluids the vessels had hitherto secreted were 



iore transparent ; but as the colour of the fluids deepen, their 



aerations and circulations are more distinctly seen. As the 



"imal thus, by the eleventh day completely formed, begins to 



f.ther strength, it becomes more uneasy in its situation, and 



i !rts its animal powers with increasing force. For some time 



fore it is able to break the shell in which it is imprisoned, it 



• heard to chirrup, receiving a sufiicient quantity of air for this 



•4rpose, from that cavity which lies between the membrane and 



e shell, and which must contain air to resist the external pres- 



e. At length upon the twentieth day, in some birds sooner, 



later in others, the enclosed animal breaks the shell, within 



II ich it has been confined, with its beak ; and by repeated ef- 

 th s, at last procures its enlargement. 



f From this little history we perceive, that those parts which 



most conducive to life are the first that are begun ; the 



V A and the back-bone, which no doubt enclose the brain and 



pi 'spinal marrow, though both are too limpid to be discerned, 



' the first that are seen to exist: the beating of the heart is 



I Reived soon after : the less noble parts seem to spring from 



jse ; the wings, the thighs, the feet, and lastly the bill. What- 



•er, therefore, the animal has double, or whatever it can live 



'ithout the use of, these are latest in production ; Nature first 



•edulously applying to the formation of the nobler organs, witli- 



)ut which life would be of short continuance, and would be be- 



!;un in vain. 



The resemblance between the beginning animal in the egg, 



nd the embryo in the womb, is very striking ; and this simili- 



ude has induced many to assert, that all animals are produced 



rom eggs in the same manner. They consider an egg excluded 



from the body by some, and separated into the womb by others, 



to be actions merely of one kind ; with this only difference, that 



2 B 2 



