37* HISTORY OF 



their secretions ; the bile is found to be separat- 

 ed, as in grown animals ; but it is fluid, trans- 

 parent, and without bitterness ; and the chicken 

 then also appears to have lungs. On the tenth, 

 the muscles of the wings appear, and the feathers 

 begin to push out. On the eleventh, the heart, 

 which hitherto had appeared divided, begins to 

 unite ; the arteries which belong to it join into 

 it, like the fingers into the palm of the hand. All 

 these appearances only come more into view, be- 

 cause 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 in- 

 creasing force. For some time before it is able 

 to break the shell in which it is imprisoned, 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 pres- 

 sure. At length, upon the twentieth day, in 

 some birds sooner, and later in others, the en- 

 closed animal breaks the shell within which it has 

 been confined, with its beak j and, by repeated 

 efforts, at last procures 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 enclose the brain, and the 

 spinal marrow, though both are too limpid to be 



