NET AVAILABLE ENERGY—MAINTENANCE. 399 
energy. The following table contains the final results, including 
those on proteids just given: 
EQUIVALENT TO 100 GRMS. OF FAT. 
Computed Found in’ 
rom . 
Dry Matter of— Metsholizable are 
Grms.’ Grms. 
Lean meat ...........-. 235 ae 
Extracted meat ......... 213 225 
234 
Cane-sugar ............. 235 235 
234 
Statchi oe csdwusaeaies 229 232 
: 258 
Grape-sugar ............ 255 254 
255 
The equivalents found by experiment correspond quite closely 
with those computed from the metabolizable energy, and on these 
facts Rubner bases the law of tsodynamic replacement, which may 
be briefly stated as follows: In amounts less than a maintenance 
ration the nutrients replace each other in inverse proportion to their 
metabolizable energy. The quantities which thus replace each other 
are accordingly said to be isodynamic. It need scarcely be pointed 
out that the minimum of proteids required for the maintenance of 
the nitrogenous tissues is not included under this law. 
Rubner is careful to limit this law to small amounts of food. 
In his earlier publications he states that it holds only below the main- 
tenance ration; later * he asserts that it obtains up to an excess of 
about 50 per cent. over the maintenance ration. 
Jsogtycosic VaLuES.—Mention has already been made of the 
theory of isoglycosic values maintained by Chauveau and his school, 
according to which the net available energy of the digested nutrients 
is measured by the amount of sugar they are considered to be capa- 
ble of producing in the organism according to the equations given 
in Chapter II. Chauveaut computes that the metabolism of 100 
parts of proteids according to Gautier’s scheme (p. 51), together 
with the partial oxidation of the resulting fat (p. 38), would yield 
* Biologische Gesetze, p. 20. + Comptes rend., 126, 1073. 
