MEMOIR OF BARON HALLER* 4? 



ressel, is alone sufficient. Instead of water and 

 other perfectly fluid elements, the enlarged vessels 

 transmit particles which are viscid and albuminous, 

 which mutually attract each other, and the nearer 

 they approach the stronger they attract. 



The manner in which the parts from heing in- 

 visible become visible, is truly simple ; it is effected 

 by enlargement, and still more by opacity. The 

 lungs become visible only on the sixth day. When 

 first perceived, they are sixteen-hundredth parts of 

 an inch long; they might have been visible when 

 only four-hundredth parts long ; but they are not 

 when eight-hundredth parts, solely because they 

 were diaphenous, and of the same colour as the 

 other parts. The liver is still larger on its first ap- 

 pearance ; and if it does not appear earlier, it is not 

 owing to its small size, but to its want of opacity. 

 It is the same with other parts; so that we should 

 be cautious in supposing that any portion of an 

 animal is newly created, or that it had no previous 

 existence : it may have been too small for observa- 

 tion, or may have been transparent. 



The movement, and apparent repose of the parts 

 of the body, depend also on the increase and opacity 

 of the parts. The heart does not appear to have 

 any movement previous to the lapse of forty-eight 

 hours. Why, it may be inquired, does motion then 

 appear ? and is it not true that the heart has pre- 

 viously propelled the fluids with vigour, since the 

 growth of the chick has been so rapid ? If the heart 

 has appeared in repose, it has been because it was 



