Art. VII. — Life as a Physical Phenomenon. By 

 George T. Stevens, M.D. 



[Read before the Albany Institute May 5, 1869.] 



Naturalists have recognized as the first step in the 

 classification of those beings of which we have knowledge, 

 three great classes or kingdoms. These kingdoms are : 

 mineral, vegetable, animal. Within these great classes 

 are included all objects which come within the limits of 

 uman observation, whether visible to the unassisted eye 

 or only revealed to vision by the aid of the most powerful 

 glasses of the microscope ; whether ponderous enough to 

 be felt or so light and infinitely diffused that they float 

 about in the atmosphere, a single volume of which out- 

 weighs a score of volumes of these subtle elements. 



Curiously enough, the elementary constituents of beings 

 in these three great divisions are in one sense common ; 

 that is, all the elements of vegetables are also found in the 

 class of minerals, and the elements of animal structures are 

 none other than those of vegetables. Indeed, certain 

 mineral elements, under certain influences, become plants; 

 and the tissues of plants under certain other influences, or 

 possibly under the same influences, differently applied, as- 

 sume the character of animals. 



Individuals, which are extreme types of each of these 

 classes, appear to indicate a most unmistakable line of de- 

 markation between the classes ; no one could fail to see 

 the dibtinction between a quadruped and a mushroom, or 

 between a rock and a rose ; but as we descend to the lower 

 orders of vegetable and animal existence, it is often a 

 question requiring the nicest discrimination to determine to 

 which of the classes a being may belong. 



