BOOKS AND CURRENT LITERATURE 221 



showed large quantities to be present in both cases, and led Volkens to 

 abandon his working hypothesis that the fall of a leaf is due to the cessa- 

 tion of the withdrawal of the products of photosynthesis through their 

 heavy accumulation in adjacent woody tissues. High sap pressure at 

 the time of foliation has been found to occur in numerous tropical trees, 

 accompanied by a slight and temporary increase in stem diameter. Using 

 this increase as a criterion of sap pressure, Volkens failed to find its 

 occurrence in any of some six trees on which measurements were made. 

 The author's general conclusions are that each species of tree has a 

 rhythmic periodicity of behavior, dependent primarily on internal physio- 

 logical conditions — and therefore subject to slight individual variations 

 in chronology — but dependent secondarily on climatic conditions. A 

 uniform climate like that of Buitenzorg permits a wide range of behavior; 

 climates with more marked seasonal differentiation show a more pro- 

 nounced marshalling of the phenomena. — F. S. 



Metabolic Water. — The subject of metabolic water, water which 

 is chemically produced within the cells of animals and plants, has recently 

 received at the hands of S. M. Babcock, 1 a much more thorough and 

 adequate treatment than we have heretofore come upon. The phenom- 

 enon of water production appears to be much more important in general 

 physiology than is usually implied in current treatises. 



The author calls attention to the well known, but usually neglected, 

 fact that large amounts of water are produced (1) by oxidation (both 

 in aerobic and anaerobic respiration) in living cells, and (2) by dehy- 

 dration of hydrated compounds. The complete oxidation of starch 

 or cellulose gives water amounting to 55.5 per cent of the original weight 

 of the material. Dextrose gives 60 per cent and most fats over 100 

 per cent. While the oxidation products from protein decomposition 

 are mainly resynthesized in plants, the production of urea and uric 

 acid from proteins in animal metabolism results in the liberation of 

 chemically formed water amounting to from 42 to 53 per cent of the 

 original weight of proteins decomposed. As examples of metabolic 

 water produced by dehydration, it may be mentioned that when glucose 

 is converted into starch or cellulose 10 per cent of the original weight 

 appears as water; while the formation of cane sugar from glucose sets 

 free water amounting to 5 per cent of the weight of glucose. Water 



1 Babcock, S. M., Metabolic Water: its production and role in vital phenomena. 

 Univ. of Wisconsin Agri. Exp. Sta. Research Bull. No. 22, pp. 87-181. March 1912. 



