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SCIENCE. 



[N. S. Vol. XIV. No. 353. 



ologists have been able to give an explana- 

 tion of the more obvious phenomena. Thus 

 locomotion, the circulation of the blood, 

 respiration, digestion, the mechanism of the 

 senses and the general phenomena of the 

 nervous system have all been investigated, 

 and in a genejal way they are understood. 

 The same statement may be made as to the 

 majority of individual organs. It is when 

 we come to the phenomena in the living 

 tissues that we find ourselves in difficulties. 

 The changes happening in any living cell, 

 let it be a connective tissue corpuscle or a 

 secreting cell or a nerve-cell, are still im- 

 perfectly understood ; and yet it is upon 

 these changes that the phenomena of life 

 depend. This has led the more thoughtful 

 physiologists in recent years back again to 

 the study of the cell and of the simple 

 tissues that are formed from cells. Further, 

 it is now recognized that if we are to give 

 an adequate explanation of the phenomena 

 of life, we should study these, not in the 

 body of one of the lower organisms, as was 

 at one time the fashion, where there is little 

 if any differentiation of function — the whole 

 body of an amceboid organism showing 

 capacities for locomotion, respiration, diges- 

 tion, etc. — but in the specialized tissue of 

 one of the higher animals. Thus the 

 muscle-cell is specialized for contraction, 

 and varieties of epithelium have highly 

 specialized functions. 



But when cells are examined with the 

 highest microscopic powers, and with the 

 aid of the highly elaborated methods of 

 modern histology, we do not seem to have 

 advanced very far towards an explanation 

 of the ultimate phenomena. There is the 

 same feeling in the mind of the physiologist 

 when he attacks the cell from the chemical 

 side. By using large numbers of cellular 

 elements, or by the more modern and fruit- 

 ful methods of micro-chemistry, he resolves 

 the cell-substance into proteids, carbo- 

 hydrates, fats, saline matter and water, 



with possibly other substances derived from 

 the chemical changes happening in the cell 

 while it was alive ; but he obtains little in- 

 formation as to how these proximate con- 

 stituents, as they are called, are built up 

 into the living substance of the cell. But 

 if we consider the matter it will be evident 

 that the phenomena of life depend on 

 changes occurring in the interactions of 

 particles of matter far too small even to be 

 seen by the microscope. The physicist and 

 the chemist have not been content with the 

 investigation of large masses of dead mat- 

 ter, but to explain many phenomena they 

 have had recourse to the conceptions of 

 molecules and atoms and of the dynamical 

 laws that regulate their movements. Thus 

 the conception of a gas as consisting of 

 molecules having a to-and-fro motion, first 

 advanced by Kronig in 1856 and by Clausius 

 in 1857, has enabled physicists to explain 

 in a satisfactory manner the general phe- 

 nomena of gases, such as pressure, viscosity, 

 diffusion, etc. In physiology few attempts 

 have been made in this direction, probably 

 because it was felt that data had not been 

 collected in sufficient numbers and with 

 sufficient accuracy to warrant any hypoth- 

 esis of the molecular structure of living 

 matter, and physiologists have been content 

 with the microscopic and chemical exami- 

 nation of cells, of protoplasm and of the 

 simpler tissues formed from cells. An ex- 

 ception to this general remark is the well- 

 known hypothesis of Du Bois-Eeymond as 

 to the existence in muscle of molecules hav- 

 ing certain electrical properties, by which 

 he endeavored to explain the more obvious 

 electrical phenomena of muscle and nerve. 

 The conception of gemmules by Darwin 

 and of biophors by Weismann are examples 

 also of a hypothetical method of discussing 

 certain vital phenomena. 



The conception, however, of the exist- 

 ence in living matter of molecules has not 

 escaped some astute physicists. The sub- 



