ANIMALS. 889 



Previous to putting the eggs to the hen, our philosophers first 

 examined the cicatricula, or little spot, already mentioned ; and 

 which may be considered as the most important part of the egg. 

 This was found in those that were impregnated by the cock to 

 be large : but in those laid without the cock, very small. It 

 was found by the microscope, to be a kind of bag, containing a 

 transparent liquor, in the midst of which the embryo was seen 

 to reside. The embrj'o resembled a composition of little threads, 

 , which the warmth of future incubation tended to enlarge by vary- 

 ing and liquefying the other fluids contained within the shell, and 

 thus pressing them either into the pores or tubes of their substance. 



Upon placing the eggs in a proper warmth,^ either under tht 

 sun or in a stove, after six hours the Altai speck begins to dilate, 

 like the pupil of the eye. The head of the chicken is distinctly 

 seen, with the back bone, something resembling a tadpole, float- 

 ing in its ambient fluid, but as yet seeming to assume none of 

 the functions of animal life. In about six hours more the little 

 animal is seen more distinctly ; the head becomes more plainly 

 visible, and the vertebrae of the back more easily perceivable. 

 AU these signs of preparation for life are increased in six hours 

 more : and at the end of twenty-four, the ribs begin to take 

 their places, the neck begins to lengthen, and the head to turn 

 to one side. 



At this time,' also, the fluids in the egg seem to have changed 

 place ; the yolk which was before in the centre of the shell, ap- 

 proaches nearer to the broad end. The watery part of the white 

 is in some measure evaporated through the shell, and the grosser 

 part sinks to the small end. The little animal appears to turn 

 towards the 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 be- 

 gun, and the animal plainly appears to move; the backbone, 

 which is of a whitish colour, thickens ; the head is turned still more 

 on one side ; the first rudiments of the ej'es begin to appear, 

 the heart beats, and the blood begins already to circulate. The 

 parts, however, as yet are fluid j but by degrees, 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 



3 Malpighi. 4. Harvey. 



