in LIVING MATTEE 89 



time, the fraction ^ = 1, Bering's metabolic equilibrium. In this 



state, the sum of the excreted substances of every kind is equal to 

 the sum of the ingested substances. 



" If the individual members of series A increase in a constant 

 relation to one another, while the members of series D remain 

 equal or decrease, so that in the unit of time the sum of the 

 members of A is greater than that of the members of D, then the 



metabolic quotient =fv>l. 



" This case is realised in growth, where the formation of living 

 substance surpasses its destruction. 



" If, vice versa, the members of series D grow proportionately to 

 one another, while those of series A remain unchanged, or become 



smaller, biotonus j*>l. This condition is the basis of atrophy, 



and leads finally to death." 



In a later work (1903) Verworn developed this theory more 

 fully, giving it the name of Biogen hypothesis and enumerating 

 the various indirect arguments, of early or recent date, which tell 

 in its favour, and show how by its application we may arrive at a 

 unitary explanation of the action of the several stimuli upon 

 living matter. 



" In my opinion " (he concludes) " the principal value of the 

 biogen hypothesis lies in the fact that it enables us to gather up 

 all the vital phenomena under a single, very definite and simple 

 point of view, without contradicting any of the facts hitherto noted. 

 This hypothesis provides us with a clear idea of the phenomena 

 fundamental to the whole of life, and is thus of singular utility 

 in facilitating the interpretation of many complex ttnd controverted 

 problems." 



" Still " (he adds) " it must once more be pointed out that this 

 is merely a working hypothesis, and that it would be quite 

 fallacious to attribute to it any other value. Whether it be a 

 faithful representation of the real facts, or whether it be in- 

 adequate, matters little ; as a working hypothesis it keeps its 

 value so long as it is useful and fecund in the progress of science. 

 The history of science is richer in fallacies than in truth ; but in 

 the development of the human mind a fertile error is of infinitely 

 greater value than a sterile fact." 



BIBLIOGRAPHY 



In addition to the general treatises on animal and plant physiology cited above 



see : 



PFLUGER. Pfliigers Arch. x. 1875. 



Cl. BERNARD. Le9ons sur les phenomenes de la vie commune aux animaux et aux 

 vegetaux. Paris, 1878-79. 



E. HERING. Vorgange d. lebender Materie, " Lotos," ix. 1888. (English transla- 

 tion, Theory of the Functions of Living Matter, by F. A. VVelby. Brain, 

 xx. 1897.) 



