METHODS OF INVESTIGATION. 239 
HEATS OF COMBUSTION OF ORGANIC SUBSTANCES (Continued). 
Rarthelot Thompson-Stohmann Method. 
Stoh- | Stoh- 
Berthe- cee Dace B. Rub- 
lot and] “and and | Dani-| jer, | Gibson. 
Asso- | Lang- | Asso- | lewski. . 
ciates. | bein. | ciates. 
6. Polysaccharids: 
Glycogen. sec cs ews ye es ene e |eaw oes 4190.6 
Cellulose .............0-2-- 4200 |4185.4| 4146 
SUALCH: 2 cscs Goacevetscareaendstnec ode 4228 |4182.5] 4123 |......]...... 4164 
DGXtPAN. 6.is-scjaee vane es Gade 4180 .4)4112.3 
Tlie cs 3 Satie iets padaeens 4187 .1/4133.5] 4070 
ALCOHOLS. 
Ethyl alcohol eat Ra 
Glycerin.............. as 4112.4] 4317 
Mannite ..........---.--2 eee .2/3997 8] 3908 |......]...... 3959 
TROSItE: 6,6 sieeve ata Genes as .8/3679 .6 
AcIDs 
ACEC sis nc eetane se Re cae aes eg 3490.4 
Palmitie:...2200002 va gee vanes dlexes oe 9352.9] 9226 
Stearic. 3 4.5.c2 pan ce ae tet ee Pa a eeas Slaw a weehs 9429 
Ole ae certs conten! Gia eamniacaso aie sd | a reatie 9494.9 
MSlORIG 5. sicotirct aca s «wear 1998 .2)...... 1960 
SBUCCIIO ae diwcsen ds manera ese 3006.2)...... 3019 
Tartare: os eiea sae insiashie e-ndoee [eu ale ¥ ee ae 1745 
CHING ec ev ieg ees a eo Ye Oe EHS 2477 .9)...... 2397 
parison. Just as the chemical analysis shows the total amounts 
of various substances or classes of substances present, so the heat 
of combustion shows the total amount of potential energy which 
has been stored up in the feeding-stuff. In both cases the knowl- 
edge thus acquired must be combined with data, secured in an 
entirely different way, as to the availability of these ingredients or 
this energy before we can form a judgment as to the relative values 
to the animal. 
Computation oF Heats or Compustion.—The heat of com- 
bustion of a mixture of various organic substances, such as are 
contained in ordinary foods and feeding-stuffs, is equal to the sum of 
the heats of combustion of the single ingredients. If the latter are 
known we may obtain the heat of combustion of the material in 
question either by a direct calorimetric determination or by deter- 
mining chemically the proportions of the several ingredients and 
multiplying the amount of each into its known heat of combustion. 
