RESPECTING VITAL MOTION. 7 



any way commensurate with that which is witnessed 

 in these organic solids. 



Notwithstanding this peculiarity, however, it is 

 evident that the simple vital movements of which we 

 speak are connected with, and in some degree deter- 

 mined by, ordinary heat, and on further examination 

 we find no reason to doubt this conclusion. 



It is found, indeed, that various inorganic solids 

 are affected differently by heat, some being acted 

 upon to a much greater extent than others: and 

 this is sufficient to show that there may be a still 

 further difference in organic substances, without any 

 departure from the mere physical character of the 

 phenomenon. 



It may be observed, also, that the solids in question 

 are composed of several elements, as oxygen, hydrogen, 

 nitrogen, and carbon, which for the most part remain 

 gaseous when in an uncombined state, and of which 

 the mutual affinity is so feeble that they readily pass 

 into an aeriform condition, and hence it may be 

 supposed that such solids will undergo a greater 

 change of volume under the action of heat than an 

 inorganic substance, in which the constitution is simple 

 and the molecular affinity more stable. And for the 

 same reason it need be no ground of wonder that 

 the change should be greater than in water, or in 

 any other fluid whose particles do not tend to 



