NATURAL PHILOSOPHY. 153 



thrown into the saino state of vibration by aerial vibrations corre- 

 sponding to the same note. Suppose now a portion of space to 

 contain a great number of such stretched strings, forming thus the 

 analogue of a "medium." It is evident that such a medium on 

 beinc agitated would give out the note above mentioned ; while on 

 the other hand, if that note were sounded in air at a distance, the 

 incident vibrations would throw the strings into vibration, and con- 

 sequently would themselves be gradually extinguished, since other- 

 wise there would be a creation of vis viva. The optical application 

 of this illustration is too obvious to need comment. 



PROGRESS OF PHYSIOLOGY. 



Lord "Wrottesley, as President of the late meeting of the British 

 Association at Oxford, in his inaugural address, remarked : — 

 " In the recent Progress of Physiology, I am informed that the 

 feature perhaps most deserving of note on this occasion, is the more 

 extended and successful application of chemistry, physics, and the 

 other collateral sciences, to the study of the animal and vegetable 

 economy. In proof, I refer to the great and steady advances 

 which have, within the last few years, been made in the chemical 

 history of nutrition, the statics and dynamics of the blood, the in- 

 vestigation of the physical phenomena of the senses, and the electri- 

 city of nerves and muscles. Even the velocity of the nerve-force 

 itself has been submitted to measurement. Moreover, when it is 

 now desired to apply the resources of geometry or analysis to the 

 elucidation of the phenomena of life, or to obtain a mathematical 

 expression of a physiological law, the first care of the investigator is 

 to acquire precise experimental data on which to proceed, instead of 

 setting out with vague assumptions, and ending with a parade of 

 misdirected skill, such as brought discredit on the school of the 

 mathematical physicians of the Newtonian period. 



" But I cannot take leave of this department of knowledge without 

 likewise alluding to the progress made in scrutinizing the animal and 

 vegetable structure by means of the microscope — more particularly 

 the intimate organization of the brain, spinal cord, and organs of the 

 senses ; also to the extension, through means of well-directed experi- 

 ment, of our knowledge of the functions of the nervous system, the 

 course followed by sensorial impressions and motorial excitement in 

 the spinal cord, and the influence excited by or through the nervous 

 centres on the movements of the heart, blood-vessels, and viscera, 

 and on the activity of the secreting organs — subjects of inquiry, 

 which, it may be observed, are closely related to the question of the 

 organic mechanism whereby our corporeal frame is influenced by 

 various mental conditions." 



THE PYRAMID OF NATURE. — ORGANIC FORCES. 



Prof. Leconte, of South Carolina College, closes an elaborate 

 paper on the Correlation of Force, with these inferences : — 



The most natural condition of matter is evidently that of chemical 

 compounds, i.e., the mineral kingdom. Matter separated from force 



