215 



each side. By this configuration they easily cat 

 the water, and are drawn forward, to take their 

 stroke backward : and by this, their feet being moved 

 to the right or left, serve them as a rudder to turn 

 under water. How they rise above water is not de- 

 termined : whether by their natural lightness, or by 

 striking against the bottom, in the manner of a leap, 

 or by some peculiar motion of the legs. That they 

 dive to the bottom is undeniable. For in the sto- 

 machs, both of the greater and lesser kind, we find 

 much grass and other weeds ; and in the lesser kind, 

 little else. Yet both prey upon fish ; and their bills 

 are straight and sharp, for the easier striking their 

 prey. 



It is likewise remarkable, that whereas in other 

 animals the lungs are loose and have much play, 

 in all birds they adhere to the thorax, and have 

 little play* This is a good provision for their steady 

 flight. Also they want the diaphragm, and instead 

 thereof have divers large bladders, made of thin trans. 

 parent membranes, with pretty large holes, out of 

 one into the other, These membranes serve for bra- 

 ces to the viscera, as well as to contain air. Toward 

 the upper part, each lobe of the lungs is perforated in 

 two places, with large perforations; whereof one is 

 toward the outer, the other toward the inner part of 

 the lobe. Through these perforations the air has a 

 passage into the fore-mentioned bladders so that by 

 blowing into the windpipe, the lungs are raised, and 

 the whole belly blown up. This doubtless is a means 

 to make them more or less buoyant, as they take in 

 more or less air : and so answers the design of the 

 air-bladder in fishes. 



In general we may observe, whatever is peculiar in 

 the wings, bills, and every other part of birds, on a 

 close inspection will be found exactly suited to their 

 wants. They are a set of implements nicely propor- 

 tioned to their manner of life. To instance in a few, 



