274 
OUR KNOWLEDGE OF 
more called attention to the importance of chemistry to medicine, 
was a period of comparative barrenness. Men were chiefly 
attracted, for the time, by visions of gold-making, and, in con- 
sequence of that and the obscure style of the records they have 
left, we have gained little by their labours. Paracelsus, however, 
having again directed attention to the importance of chemistry 
as a medical art, may in some degree be regarded as 
having initiated a new era. He was followed by others of 
similar spirit, and about two hundred years ago, (1069 to 1682,) 
Becher and Stahl propounded a great chemical hypothesis. 
This was the theory of phlogiston, which flourished ex- 
ceedingly for nearly a century, but can hardly he said to have 
promoted chemistry, overlooking, as it unfortunately did, the 
fundamental law of the science, viz., the indestructibility of 
matter. 
Ihe phlogistians regarded all combustible substances as 
composed of a fixed earth or calx, and a fiery principle or 
phlogiston. In combustion the phlogiston was said to escape 
under the form of flame, (flame being phlogiston in a state 
of vibration,) leaving behind the ash or calx. To-day we 
see there was much truth in this, bodies when burnt do lose 
something, which we regard not as a form of matter, but as what 
is commonly termed “ energy,'’ which here takes the form of 
heat. The phlogistians knew that if the calx of iron or any 
other metal were heated with a highly combustible body, as, 
for example, oil or charcoal, it recovered its combustibility and the 
other properties of the metal, and hence they concluded that 
in each case the phlogiston of the oil or charcoal had united 
with the calx of the metal. Thus the hypothesis appeared for 
a long while to explain the nature of combustion, to show an 
analogy in the nature of the various combustible bodies, and 
also to give a satisfactory account of the chemistry of metal- 
lurgical operations. 
