768 THE POPULAR SCIENCE MONTHLY. 



cal and physical forces for those proximate constituents which go to 

 nourish and build up the tissues and enable the organs of the body to 

 perform their respective functions. 



In nutrient action, by which lifeless material or pabulum is trans- 

 formed into living tissues, evidence of this vital entity should be dis- 

 covered, if anywhere, for here we have the primal seat of life, the very 

 fountain of genetic power. 



Analysis, however, finds room for it in nutrient action no more 

 than in the mysteries which lie concealed in every expression of energy 

 throughout nature's domain. Why will friction of glass produce a 

 condition or property which will repel pith-balls, while friction of 

 sealing-wax produces a condition which will attract them ? Are these 

 movements caused by some kind of life-principle developed in so sim- 

 ple a way ? No ; they come from positive and negative electricity 

 evolved by friction, and, with this answer, science asserts that the ex- 

 planation is complete. When asked, What is electricity, beyond a 

 special display of energy ? there is no answer. 



If we question the various organic functions of the body, physical 

 and chemical forces alone confront us. A muscle contracts according 

 to mechanical laws, and its work is expressed in mechanical equiva- 

 lents. Electric tension is lost, heat is evolved, carbon dioxide appears, 

 and the muscular tissue, before neutral in reaction, is now acid. What- 

 ever may be the nature of the vital force, if such there be, operating 

 in muscular contraction, it at least is not independent of physical and 

 chemical forces, and the evidence is cumulative that these will alone 

 explain the phenomenon. Respiration is purely a chemical process, in 

 harmony with the laws of gaseous diffusion. Circulation, with its 

 pumps, pipes, and valves, is an hydraulic operation. Absorption is os- 

 motic, and a similar selective affinity for special things is exhibited in 

 inorganic material as well as in animal membranes. 



There seems no good reason why we should hesitate to regard the 

 vital force as correlated with the physical forces known to us as heat, 

 light, electricity, and actinism. That some relation exists there can 

 be no doubt, for the effect of physical forces upon organic life is 

 marked, and their energy is made potential in the tissues of both vege- 

 tables and animals. This potential energy is, after a time, transformed 

 into active energy, and new phenomena result. 



Organic forms do not generate energy, they simply transform or 

 evolve it from that which has been supplied from the outer world. 

 Heat in the body results from combustion the same as in a furnace. 

 - Contractility is a special function of muscular tissue, and is inde- 

 pendent of nerve-force. This attribute exists in the tissue for a time 

 after death, lasting longer in cold-blooded than in warm-blooded ani- 

 mals, because of the slowness of the process of the destructive assimi- 

 lation of the tissues. Longet demonstrated that contractility is closely 

 related to the supply of arterial blood in the capillary vessels, for, on 



