26 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



By the distinguished labors of Kinil Fischer 1 even the structure of carbohy- 

 drate bodies lias been determined, and bodies belonging to this group have 

 been synthetically constructed in the laboratory. Moreover, the work of 

 Schiitzenberger, Grimaux, and Pickering gives promise that before long pro- 

 teid bodies may be produced by similar methods. Physiologists have shown, 

 furthermore, that the digestion that takes place in the stomach or intestine 

 may be effected also in test-tubes, and at the present day probably no one 

 doubts that in the act of digestion we have to deal only with a series of 

 chemical reactions which in time will be understood as clearly as it is possible 

 to comprehend any form of chemical activity. Indeed, the whole history of 

 food in the body follows strictly the great physical law- of the conservation 

 of matter and of energy which prevail outside the body. No one disputes 

 the proposition that the material of growth and of excretion comes entirely 

 from the food. It has been demonstrated that the measureable energy given 

 off from the body is all contained potentially within the food that is eaten. 2 

 Living things, so far as can be determined, can only transform matter and en- 

 ergy ; they cannot create or destroy them, and in this respect they are like inan- 

 imate objects. But, in spite of the triumphs that have followed the use of the 

 experimental method in physiology, every one recognizes that our knowledge 

 is as yet very incomplete. Many important manifestations of life cannot be 

 explained by reference to any of the known facts or laws of physics and 

 chemistry, and in some cases these phenomena are seemingly removed from 

 the field of experimental investigations. As long as there is this residuum 

 of mystery connected with any of the processes of life, it is but natural that 

 there should be two points of view. Most physiologists believe that as 

 our knowledge and skill increase these mysteries will be explained, or rather 

 will be referred to the same great final mysteries of the action of matter and 

 energy under definite laws, under which we now classify the phenomena of 

 lifeless matter. Others, however, find the difficulties too great, — they perceive 

 that the laws of physics and chemistry are not completely adequate at present 

 to explain all the phenomena of life, and assume that they never will be. 

 They suppose that there is something in activity in living matter which is 

 not present in dead matter, and which for want of a better term may be desig- 

 nated as vital force or vital energy. However this may be, it seems evident 

 that a doctrine of this kind stifles inquiry. Nothing is more certain than the 

 fact that the great advances made in physiology during the last four decades 

 are mainly owing to the abandonment of this idea of an unknown vital force 

 and the determination on the part of experimenters to make the greatest pos- 

 sible use of the known laws of nature in explaining the phenomena of life. 

 There is n<> reason to-day to suppose that we have exhausted the results to be 

 obtained by the application of the methods of physics and chemistry to the 

 study of' living things, and as a matter of fact the great bulk of physiological 

 research is proceeding along these lines. It is interesting, however, to stop 



1 Die Chemieder Kohlenhydrale, Berlin, 1S94. 

 2 Kubner : Tkitschrift fur Biologic, Bd. xxx. 8. 73, 1894. 



