336 LUDWIG AND MODERN PHYSIOLOGY. 



infinite complication of parts and powers, unfolds the plan of its exist- 

 ence — taken with the observation that that small beginning was, in all 

 excepting the lowest forms, itself derived from two parents, equally 

 from each — is the basis from which his study and knowledge of the 

 world of living beings takes its departure. For on these two facts — 

 evolution and descent — the explorer of the forms, distribution, and 

 habits of animals and plants has, since the Darwinian epoch, relied 

 with an ever-increasing certainty, and has found in them the explana- 

 tion of every phenomenon, the solution of every problem relating to 

 the subject of his inquiry. Nor could he Avish for a more secure basis. 

 Whatever doubts or misgivings exist in the minds of "nonbiologists" 

 in relation to it may be attributed partly to the association with the 

 doctrine of evolution of questions which the true naturalist regards as 

 transcendental, partly to the perversion or weakening of meaning 

 which the term has suffered in consequence of its introduction into the 

 language of common life, and particularly to the habit of applying it to 

 any kind of progress or improvement, anything which from small 

 beginnings gradually increases. But, provided that we limit the term 

 to its original sense — the evolution of a living being from its germ by a 

 continuous, not a gradual process — there is no conception which is more 

 free from doubt either as to its meaning or reality. It is inseparable 

 from that of life itself, which is but the unfolding of a predestined 

 harmony, of a prearranged consensus and synergy of parts. 



The other branch of biology, that with which Ludwig's name is 

 associated, deals with the same facts in a different way. While 

 ontology regards animals and plants as individuals and in relation to 

 other individuals, physiology considers the processes themselves of 

 which life is a complex. This is the most obvious distinction, but it is 

 subordinate to the fundamental one, namely, that while ontology has 

 for its basis laws which are in force only in its own province, those of 

 evolution, descent, and adaptation, we physiologists, while accepting 

 these as true, found nothing upon them, using them only for euristic 

 purposes, i. e., as guides to discovery, not for the purpose of explana- 

 tion. Purposive adaptation, for example, serves as a clue, by which 

 we are constantly guided in our exploration of the tangled labyrinth 

 of vital processes. But when it becomes our business to explain these 

 processes — to say how they are brought about — we refer them not to 

 biological principles of any kind, but to the universal laws of nature. 

 Hence it happens that with reference to each of these processes, our 

 inquiry is rather how it occurs than why it occurs. 



It has been well said that the natural sciences are the children of 

 necessity. Just as the other natural sciences owed their origin to the 

 necessity of acquiring that control over the forces of nature without 

 which life would scarcely be worth living, so physiology arose out of 

 human .suffering and the necessity of relieving it. It sprang, indeed, 

 out of pathology. It was suffering that led us to know, as regards our 



