loo THEORETICAL BIOLOGY 



investigation, physics and chemistry assist one another in 

 the study of matter. 



But chemistry is also an ancient science, carefully nur- 

 tured through the Middle Ages by the astrologists, who have 

 been most unjustly decried. 



In comparing mediaeval chemistry with that of the present 

 day, we might easily suppose that we were dealing with two 

 distinct sciences ; but the investigators of those times were 

 trying, just like the modern chemists, to discover what are 

 the properties and capacities belonging to the various forms 

 of matter. 



They studied not only the structure of matter, but also 

 its other properties, and asked such questions as " What is 

 its colour ? ", " What sort of a sound does it give ? ", " What 

 does it taste like ? ", " What does it feel like to the touch ? ", 

 and " How heavy is it ? " 



For in principle we ascribe to every substance one quality 

 from each of the sense-scales ; and if it cannot be demon- 

 strated, we do not assume that the substance has not got the 

 quality, but we say, for instance, " Smell or taste not per- 

 ceptible." 



In considering the sense-qualities in their relation to the 

 local signs, we may, as has been explained, regard the latter 

 as the smallest receptacles that have the sense-qualities as 

 content. With the local signs we might therefore contrast the 

 sense-qualities as content-signs. It is only when the two are 

 in association that we have " matter.*' 



The old chemistry and the new alike endeavour to separate 

 the forms of matter from one another and investigate them 

 (and consequently all the accessible content-signs of matter in 

 all possible conditions), so as to get as exact a notion as 

 possible of all the properties and capacities of each individual 

 substance. 



The mediaeval chemist looked at a substance, touched it, 



