A HISTORY OF METABOLISM 11 



Willis (1621-1675), a contemporary of Boyle, and his pupil Lower, 

 a colleague of Mayow at Oxford, demonstrated the reddening of blood 

 by the respiration by admitting and excluding air from an animal. 



Stephen Hales (1677-1761) was a parish priest described by Horace 

 Walpole as "a poor, good, primitive creature." And yet this apparently 

 unimportant man writes in his "Statical Essays," published in 1727, 

 "A part of the inspired air is lost in the blood, but it is as yet entirely 

 dark what its use may be." 



Boerhaave (1668-1738), when he published his great work, the 

 "Elements of Chemistry," in 1724, is believed to have had the work of 

 Mayow in mind when he wrote: "Who can say whether an air of spe- 

 cial virtue for the maintenance of the lives of animals and plants does 

 not exist; whether it may not become exhausted; whether its consump- 

 tion is not the cause of the death of animals who can no longer possess 

 it ? Many chemists have announced the existence of a vital element in 

 the air, but they have never told what it is or how it acts. Happy the 

 man who discovers it!" 



Stahl (1660-1734), the German chemist who in 1716 moved to Berlin 

 as physician to the King of Prussia, was the originator of the phlogiston 

 theory of combustion which enthralled the minds of men for nearly a 

 hundred years. According to this theory all combustible substances con- 

 tained phlogiston which passed from them when they were burned. What 

 we now know as oxids of iron or lead 'were those metals which through 

 burning had lost their phlogiston. Such substances, if calcined with 

 carbon, a material supposed to be rich in phlogiston, absorbed phlogiston 

 and became metals once more. This simple theory availed to explain all 

 the phenomena of combustion and was generally accepted by the scientific 

 world. 



When one halts to consider the general knowledge of nutrition in 

 the middle of the eighteenth century one finds little to distinguish be- 

 tween the statements of Sanctorius, 150 years earlier, and Benjamin 

 Franklin. Sanctorius writes, "Meats which promote Perspiration bring 

 Joy, but those which obstruct it Sorrow"; and Franklin in 1742, "If 

 thou art dull and heavy after Meat it is a sign that thou hast exceeded 

 due measure; for Meat and Drink ought to refresh the Body and make 

 it cheerful and not to dull or oppress it." 



The general opinion of high authorities in the eighteenth century was 

 voiced by Haller. 



Albrecht von Haller (1708-1777), the great physiologist, published 

 his "Elementa Physiologica" between 1757 and 1765. He asserts "that 

 fire is contained in the blood is proved by its heat," and he has this 

 rather hazy conception of the process of respiration: "The secondary 

 uses of respiration are very numerous. It exhales copiously and removes 

 from the blood something highly noxious; for by remaining in the air 



