376 O F I N F A N C Y. 



that mental fenfation commences not fooner 

 than 40 days after birth j for fmiles and tears 

 are the effcds of two internal fenfations, which 

 both depend upon the adion of the mind. The 

 former is an agreeable fcnGition, which origi- 

 nates from the fight or remembrance of a 

 known and defirable object : The latter is a dif- 

 agreeable agitation, compounded of fympathy 

 and anxiety concerning our own welfare. Both 

 thefe pafTions prefuppofe a certain degree of 

 knowledge, and a power of refleding, and of 

 comparing ideas. Smiles and tears are expref- 

 fions of pleafure and pain peculiar to the hu- 

 man fpecies ; for the cries, the motions, and 

 the other marks of bodily pains and pleafures, 

 are common to man and moft of the other ani- 

 mals. 



But we muft now return to the material or- 

 gans and afi'eQions of the body. The fize of an 

 infant born at the full time is generally about 

 21 inches, though fome exceed, and others fall 

 much below this ftandard. The breaft of a 

 child of 2 1 inches, meafured by the length of 

 the fternum, is about three inches, and only 

 two, when the infant exceeds not 14 inches in 

 length. At nine months, a foetus generally 

 weifihs from 12 to ia pounds. The head is 

 large in proportion to the hodj ; but this dif- 

 proportion gradually wears oiT, as the infant in- 

 preafes in iize. The flvin of a new-born child 

 -is very fme, and of a reddilh colour, its tranf^ 



parcncv 



