Ikiv introductory observations* 



infenfible parts, the hair, the nails, the fkin, are 

 conftantly falling off and produced again. Some 

 parts regenerate only once Or twice during life , 

 others hardly ceafe before the reprodu^ive fa- 

 culty is loft for ever. 



Several parts of the body are acquired after 

 birth. Then the teeth of mankind feldom exift. 

 In a few years, thofe firft expanding are loft and 

 replaced by others, which remain ferviceable 

 until decayed by time. Sometimes, at a very 

 advanced age, a new fet appears, even at an 

 age which few live to attain ; and thefe, whofe 

 germs have exifted a century in the perfon, (if 

 germs or organs are not created,) are as found 

 and entire as in the moft vigorous and youthful. 

 The hair grows rapidly after birth ; it is continu- 

 ally deftroyed and conftantly reproduced, and 

 in fuch a manner that it will frequently branch 

 afunder. This is the common courfe repeatedly 

 in a year ; but it is very remarkable, that, after ten 

 or twelve years, it begins only then to grow on 

 particular parts of the body : and after it fprings, 

 there feems to be very little reproduction. The 

 nature and properties of this fubftance are as yet 

 but imperfectly underftood. The renewal of the 

 ikin is almoft infenfible ; it comes off in minute 

 fcales. One inftance occurred vwhere the whole 

 {kin of both hands, up to the wrift, was thrown 



eft 



