!255 
will still remain barren and unproductive, if not 
quickened into life by the pervading energy of the 
mind. This " commercium mentis et rerum," it 
was, indeed, the great aim of Lord Bacon's philosophy 
to promote. " For thoughts," says one of his ear- 
liest disciples, " cannot work upon nothing^ no more 
than hands. He that would build a house, must 
provide materials ; and, on the contrary, the mate- 
rials will never become a house, unless, by certain 
rules, we join them all together. So, it is not simply 
the knowledge of many things, but a multifarious 
copulation of them in the mind, that becomes prolific 
of farther knowledge *." 
541. Concerning the respiration of insects, we be* 
fore remarked (51.), that the ancients observed these 
animals to die when their bodies were smeared over 
with oil, which effect Mr Ray rightly attributed to 
the " interceding of the ain" Mr Boyle, among 
the almost innumerable experiments which he made 
with the air-pump, found, that flies, bees, and butter- 
flies died in a few minutes when the receiver was ex- 
hausted of its air. It was notable also, he adds, that 
though bees and flies will walk and fly a great while 
after their heads are cut off, or even one half of the 
body move several hours after being severed from 
the other, yet, upon the exsuction of the air, not only 
the motion of the body, but of the limbs, ceases, as 
if the presence of air were more necessary than that 
of their own heads f. 
* Crew's Anut. oi Plants, p. 8. 
I Boyle's Works, 4to, vol. i. p. 79, 1 1C. 
