37 



pump and in the open air. They may 

 also be excited linger water, under oil, 

 in a great variety of gases; in short, under 

 circumstances which exclude the presence of 

 any chemical agent from without, to which 

 such changes could reasonably be imputed. 



Secondly. The contraction of irritability 

 has been supposed to be a property of the 

 muscular fibres. Properties are generally 

 considered as permanent qualities. Thus, 

 the property of gravitation is continually 

 operating, equally when bodies remain at 

 rest and when it produces motion in them, 

 equally whilst I support this book in my 

 hand, and when I suffer it to fall on the 

 table. If, however, so curious an occa- 

 sional property could belong to matter, 

 we should naturally expect that it would 

 belong to some peculiar quality, or ar- 

 rangement of matter. But irritability is 

 connected with matter of different quali- 



