252 ON GENERATION. 



EXERCISE THE NINETEENTH. 



The fifth inspection of the egg. 



On the sixth day the three cells of the head present them- 

 selves more distinctly, and the coats of the eyes are now ap- 

 parent ; the legs and the wings also bud forth, much in the way 

 in which, towards the end of June, we see tadpoles getting 

 their extremities, when they quit the water, and losing their 

 tails assume the form of frogs. 



In the chick, the rump has still no other form than is con- 

 spicuous in animals at large, even in serpents ; it is a round and 

 slender tail. The substance of the heart now grows upon the 

 pulsating vesicle ; and shortly afterwards the rudiments of the 

 liver and lungs are distinguished; the bill, too, makes its ap- 

 pearance at the same time. Everything is of a pure white co- 

 lour, especially the bill. About the same epoch all the viscera 

 and the intestines are conspicuous. But the heart takes 

 precedence of all the parts ; and the lungs are visible before the 

 liver or brain. The eyes, however, are seen first of all, by 

 reason of their large size and black colour. 



And now, too, the embryo has a power of motion, and raises 

 its head and slightly twists itself, although there is still nothing 

 of the brain to be seen, but only a little limpid fluid inclosed 

 in a vesicle. It is at length a perfect maggot, only differing 

 from a caterpillar in this, that when worms are set free from 

 their cells they creep about hither and thither and seek their 

 food, whilst the worm in the egg is stationary, and, surrounded 

 with its proper food, is furnished with aliment through the 

 umbilicus. 



The viscera and intestines being now formed, and the foetus 

 able to execute motions, the anterior portion of the body, with- 

 out either thorax or abdomen, is perceived to be completely 

 open ; so that the heart itself, the liver and the intestines, are 

 seen to hang pendulous externally. 



Towards the end of this day and the beginning of the seventh, 

 the toes are distinguished, and the embryo already presents the 

 outlines of the chick, and opens its beak, and kicks with its 



