8 PHYSIOLOGY 



science of the living ; it always signifies a process that either 

 tends to apply the mechanical explanation to a supposed vital 

 phenomenon, or brings out the essentially vital character of a 

 supposed physico-chemical phenomenon. 



The evolutionary process of physiological science has always 

 been in the past, and will always be in the future, a continuous 

 and fruitful struggle between the two opposite tendencies of 

 Materialism and Vitalism. It is a mistake to suppose that either 

 the one or the other will ever win the final victory. Both are 

 one-sided ; both reflect one face only of reality. Life, in its more 

 highly evolved forms, results from their interpenetration and 

 fusion. Seen from without, it is })ody : felt from within, it is 

 soul : this is the great mystery that Art for ever celebrates ra 

 mystery Science, with every possible and conceivable progress 

 in physics and chemistry, with all the experimental methods that 

 it may or might employ, will never be in a position to solve. 



IV. As the physico-chemical science of living beings, Physiology 

 includes the comparative study of the vital phenomena of plants, 

 animals, and man. 



Some vital phenomena are common to all living beings, 

 without distinction of species, genera, classes, or kingdoms. These 

 are fundamental phenomena, that is, they are the simplest and 

 most elementary in life. Their material substratum -is the Cell, i.e. 

 the simplest morphological unit, which Briicke calls the elementary 

 organism, whether living its independent life, or living in 

 association with other cells to form cell aggregates or complex 

 organisms. 



The physiology of the cell lies at the foundation of all 

 physiology, because the functions of the tissues, organs, and 

 systems can ultimately be reduced to the vital activity of the 

 various cells from which they evolve. Plant physiology, as well 

 as animal and human physiology, derive the fundamental data 

 relating to elementary functions from the physiology of the cell, 

 and employ it as a basis in their study of the complex and special 

 functions of the several tissues, organs, and systems. 



The science of physiology calls for a different arrange- 

 ment and development, and may assume a different aspect and 

 even content, according as it is approached from a scientific, 

 a philosophical, or a medical and practical standpoint. From 

 the first two it assumes the form and content of general and 

 comparative physiology, which is the necessary complement of 

 general and comparative morphology; both are directed to the 

 high aim of illustrating, tabulating, and developing the grand 

 doctrine of Evolution or Descent, which from Darwin onwards has 

 been undergoing constant transformation and integration. From 

 the third it assumes the form and content of human physiology, 

 taking Man as the goal of its investigations; it harvests the 



