CONNEXION OF THE SCIENCES. 31 



yet let there be an entire freedom from all such preju- 

 dices as would shut you up from the reception of truth 

 from any and every quarter whence it may present 

 itself. 



Learn so correctly to appreciate things, that while 

 you entertain the full persuasion that professional know- 

 ledge is essential to your success, you believe also that 

 there is no species of knowledge but what may be turned 

 to beneficial account. All, in truth, are parts of one 

 grand whole, which, though they have been separated 

 into distinct departments for their more ready and 

 effectual cultivation, as well as that every individual 

 may appropriate his own regions of investigation, 

 according to his peculiar bias, are attached to each 

 other by points of contact more or less numerous ; so 

 that light thrown upon one region inevitably sheds more 

 or less of its illumination over others. 



A single example may suffice for the illustration of 

 this. From a momentary glance of thought you might 

 be inclined to doubt if you were told that an intimate 

 connexion subsisted between the sciences of anatomy 

 and vegetable physiology, and portions of acoustics, 

 chemistry, hydraulics, mechanics, optics, and pneu- 

 matics; and yet if you direct your thoughts a little 

 onward, and wish to comprehend the structure of the 

 eye, the nature of its separate "humours," as they 

 are technically designated, and the theory of vision, 

 you will at once perceive that you must have re- 

 course to optics and chemistry; and, in like manner, 

 to comprehend the structure and functions of the 

 ear, you must have recourse to acoustics ; to compre- 

 hend the force and operations of the joints and muscles, 

 you must turn to mechanics ; the study of the blood- 



