CHAP. XIV.] 



TACTILE PAPILLA. 



409 



indicated on the outer surface by cor- 

 responding minute and very shallow 

 grooves, crossing the tops of the ridges 

 more or less at right angles. Each pair 

 of papillae thus occupies a little division 

 of the ridge. In the centre of each 

 cross line, between the pairs of papillae, 

 is observed the orifice of a sweat-duct 

 (shortly to be noticed), which often is 

 so large as to destroy the linear charac- 

 ter of the cross groove. In a square 

 inch of the palm we may generally 

 count rather more than forty rows of 

 papillae, and in each row rather more 

 than sixty pairs of them. 



In the natural state the papillae are 

 intimately united at all points of their 

 surface to the epidermis which invests 

 them. By a slight maceration this 

 union may be so loosened that the two structures may be readily 



JYgr.79. 



I) 



Under-surface of the cuticle, detached by maceration from the palm ; showing the double rows of 

 depressions in which the papillae have been lodged, with the hard epithelium lining the sudoriferous 

 ducts in their course through the cutis. Some of these are contorted at the end, where they have 

 entered the sweat-gland Magnified 30 diameters. 



