884 



SCIENCE 



[N. S. Vol. XXXIV. No. 



not as widely appreciated as it deserves to be. 

 There are few comparable or equally compre- 

 hensive outlines of the subject published in 

 English. This chapter may serve also to 

 illustrate the effectiveness of the revision 

 which has been practised in the new edition. 

 Not only are new facts introduced (American 

 investigations not being overlooked), but dis- 

 carded and unsubstantiated views have been 

 conservatively eliminated. For example, there 

 are found detailed allusions to the studies in 

 " artiiicial " nutrition, Michaud's experiments 

 on the protein minimum, Eubner's recent dis- 

 cussions on nutrition, Murlin's study of gela- 

 tin feeding, and the disputed problem of the 

 specific dynamic action of foods. The discus- 

 sion of obsolete obesity " cures," etc., has been 

 omitted. 



In the translator's preface Professor Mandel 

 writes : " The work of translating and editing 

 has been a labor of love, inasmuch as I feel 

 that it will be of aid in the advance of this 

 department of chemical science." He is right, 

 and deserves a renewed expression of appre- 

 ciation from biochemical workers for the 

 faithful and correct execution of an unin- 

 viting task. 



Lafayette B. Mendel 



Sheppield Scientific School, 

 Yale University 



SPECIAL ABTICLES 



ON THE NATURE AND SEAT OF THE ELECTROMOTIVE 

 FORCES MANIFESTED BY LIVING ORGANS^ 



1. When an organ of an animal or a plant 

 is injured an electromotive force develops be- 

 tween the injured and the non-injured surface, 

 the latter being, as a rule (if not always), 

 positive to the former. Loeb suggested in 

 1897 that this difference of potential might be 

 due to the fact that the injured spot formed 

 an acid and that on account of the H-ion 

 moving faster than the anion a difference of 

 potential was produced. This assumption ac- 

 counted for the sense of the E.M.F. in a par- 

 tially injured organ. It was, however, pointed 

 out that the order of magnitude of such dif- 



' Preliminary communication. 



fusion elements is too small to account for the 

 E.M.F. found in living organs. Wilhelm 

 Ostwald had suggested the possibility that 

 living organs form concentration elements 

 with a solid phase interposed, the solid phase 

 — the membrane — ^being permeable for certain 

 ions only. Bernstein starting from Helmholtz's 

 conception of free energy conceived the idea 

 that measurements of the effect of tempera- 

 ture on the E.M.F. of a partially injured 

 muscle or nerve might indicate the nature of 

 the elements to which these systems belong. 

 He reached the conclusion that the partially 

 injured muscle belongs to the tjpe of concen- 

 tration element in which a solid phase — the 

 membrane — separates the two liquids, the solid 

 phase being only or more permeable to kations 

 than to anions, thus corroborating Ostwald's 

 suggestion. 



Bernstein found that the E.M.F. of the 

 muscle rises in general with the temperature 

 and that it approaches a value in proportion 

 to the temperature. The agreement was, how- 

 ever, not as good as should be desired to put 

 the theory of concentration cell of the muscle 

 current on an absolutely safe basis. More- 

 over, experiments on nerve were less satisfac- 

 tory and in both cases accessory assumptions 

 were required to make the actual results agree 

 with the theory. 



2. Muscles and nerves are, perhaps, too 

 variable or rather perishable to investigate 

 quantitatively with any degree of satisfaction 

 the nature and origin of their E.M.F. We 

 selected for this purpose a hardier and more 

 constant object, namely, apples, the surface 

 film of which is strong and which remains 

 siiificiently constant during such an investi- 

 gation. Instead of testing the effect of tem- 

 perature on the E.M.F., we selected the effect 

 of the concentration of the solutions in con- 

 tact with the apple. The limit within which 

 the temperature can be safely changed with- 

 out injuring or modifying the living organ is 

 very small and this is one of the reasons why 

 Bernstein's figures are not quite satisfactory, 

 as he himself recognized; while we can 

 change the concentration on such living ob- 



