578 RESPIRATION A MEASURE 



pended chiefly on the brain and organs of loco- 

 motion ; whereas in the latter, a portion of the 

 blood is converted into fat, that becomes a burden 

 to its owner, and in every way detracts from the 

 energies of body and mind. Hence the observa- 

 tion of Shakspeare, thai fat ribs make lean pates. 



And if we descend to the lower orders of air- 

 breathing animals, whose mean healthy tempe- 

 rature is from 30 to 50 below that of birds* and 

 mammalia, and falls to that of the surrounding 

 medium during winter in the higher latitudes, 



* That birds consume at least twenty times more oxygen in pro- 

 portion to their weight than reptiles, would appear from some ex- 

 periments performed by Dr. Edwards, who found that a frog was 

 capable of living above three days when confined in a vessel con- 

 taining sixty-four cubic inches of common air ; fwith a solution 

 of pure potass for absorbing the carbonic acid exhaled,) whereas, 

 under the same circumstances, a yellow-hammer of the same 

 weight lived only one hour. Nor can there be a doubt that many 

 of the smaller birds devour more food in one day, than reptiles of 

 the same size in twenty. For it is well known, that frogs, toads, 

 salamanders, tortoises, and many other reptiles, are capable of 

 living several weeks without food, or suffering any material dimi- 

 nution of weight, and that serpents are often many weeks in diges- 

 ting a single meal. Spallanzani relates an instance of one that 

 was three months in completing the digestion of a fowl. He also 

 found that in snakes, the process was more rapid in June, when 

 the temperature was 82 than in April when at 60. Hence the 

 slow growth of all cold blooded animals, compared with birds 

 and mammalia. Nor can there be a doubt, that the muscular 

 power of the latter is from ten to twenty times greater than that of 

 reptiles, ceteris paribus, for example, that in a horse weighing 

 VOOlbs. it is ten times greater than in a tropical turtle of the same 

 weight, and twenty times greater in a sparrow than a frog. 



