PALMIPEDES. 175 



and partly membranous. They live on lakes and ponds, where they are 

 very destructive to fish. 



Merg. merganser, L.. (The Goosander), is the size of a Duck, and has 

 red feet and a bill of the same hue. The head of the old male is of a deep 

 green, the feathers on its summit forming- a sort of toupee; the mantle is 

 black, with a white spot over the wing-; underneath and the neck white 

 slightly tinged with rose-colour. 



CLASS III. 

 REPTILIA. 



The disposition of the heart in Reptiles is such, that at each con- 

 traction, a portion only of the blood it has received from the differ- 

 ent parts of the body is transmitted to the lungs, the remainder 

 returning to those parts without having passed through the pulmo- 

 nary organs, and without having respired. 



The result of this is, that the action of oxygen upon the blood is 

 less than in the Mammalia, and that if the quantity of respiration in 

 the latter, in which all the blood is compelled to pass through the 

 lungs before it returns to the rest of the body, be expressed by a 

 unit, that of Reptiles will be expressed by a fraction of a unit, so 

 much the smaller, as the quantity of blood transmitted to the heart 

 at each contraction is less. 



As it is from respiration that the blood derives its heat and the 

 fibre its susceptibility of nervous irritation, the blood of reptiles is 

 cold, and the muscular energy less than that of Quadrupeds, and 

 much less than that of Birds; thus we find their movements usually 

 confined to crawhng and swimming; for, though at certain times 

 several of them jump and run with considerable activity, their habits 

 are generally lazy, their digestion excessively slow, and their sensa- 

 tions obtuse. In cold or temperate climates almost all of them pass 

 the winter in a state of torpor. Their brain, which is proportionally 

 very small, is not so essentially requisite to the exercise of their ani- 

 mal and vital faculties, as to the members of the two first classes; 

 their sensations seem to be less referred to a common centre, for 



