Nipple
FIG. 1 is a front elevational view of a nipple showing our new design; 
     FIG. 2 is a rear elevational view; 
     FIG. 3 is a side elevational view; 
     FIG. 4 is a top plan view; and 
     FIG. 5 is a bottom plan view. 
     The broken line showing of the bottle is for illustrative purposes only and forms no part of the claimed design.