222 Letter to Governor Pownall 



ties bat their own. Yoii, sir, even in the new science of 

 galvanism, have advanced the sentiments of Sir Isaac New- 

 ton ; and in this letter I shall extract from a very scarce 

 work, entitled A Treatise on the Animal Economy, by Dr. 

 Bryan Robinson, (published in 1734, in Dublin, the second 

 edition,) some passages which show the advances then made 

 in chemistry and the animal oeconomy. In the preface this 

 learned writer savs : " Harvey, from experiments and ob- 

 servations, traced out the circular motion of the blood. 

 After him Lower made some further discoveries concerning 

 that motion, and the causes by which it may be disturbed. 

 After these great men, the knowledge of the animal ceco- 

 nomy received no ver)- considerable improvement till Sir 

 Isaac Newton discovered the causes of muscular motion 

 and secretion ; and likewise furnished materials for explaiu- 

 ino- diorestion, nutrition, and respiration. To him I am 

 chiefly indebted for what I have delivered on those heads." 



He then goes on, in a most ingenious and satisfactory train 

 of deep reasoning, to establish very curious and interesting 

 propositions respecting the motion of the blood, in twenty- 

 three propositions, and then proceeds to 



Proposition xxiv. — '* The life of animals is preserved by 

 acid parts of the air mixed with the blood i?i the lungs ; which 

 parts dissolve or uticnuale the blood, and preserve its heat ; 

 and by both these keep up the motion of the heart. 



" 1 shall prove the truth of this proposition from a series 

 of experiments and observations, 



"First, then, animals die when they are deprived of air by 

 stopping the wind-pipe, or putting them in an air-pump 

 and drawing out the air. And they likewise die soon in a 

 small quantity of air so closely confined as to have no com- 

 munication with the rest of the atmosphere : small birds 

 cannot live above three or four hours in a quart of such air; 

 and a gallon of air included in a bladder, and by a pipe al- 

 ternately inspired and expired by the lungs of a man, will 

 become unfit to preserve life in little more than one minute 

 of time. 



" Hence it appears that air is necessary to preserve the 

 life of animals ; and likewise, that a constant supply of fresh 

 air is necessary to that end. 



" Secondly^ A candle goes out, glowing coals and red- 

 hot iron cease to shine, and animals die, in the air-pump 

 on drawing out the air. A candle goes out, glovying coals 

 and red-hot iron cease to shine, and animals die, in a small 

 quantity of a'r so closely confined as to have no communi- 

 cation with the rest of the atmosphere. Animals die in air 



rendered 



