344 PHYSIOLOGICAL CHEMISTRY. 



sess food value in a high degree, but after a time, as the chem- 

 istry of the proteins and their derivatives became better under- 

 stood, this notion was gradually abandoned. Lean meat, mus- 

 cle, is employed practically in the process; hence little or no 

 fat can be present. At the boiling temperature nearly the 

 whole of the proteins are coagulated and are filtered out. A 

 little gelatin remains, but the food value of this is of minor 

 importance. Unless the boiling is greatly prolonged the ex- 

 tract must therefore contain essentially the meat bases and 

 other extractives referred to above, and the actual nutritive 

 value of these is low, in the case of the bases being nil. On 

 prolonged boiling, however, a small portion of the original 

 protein seems to pass over into the soluble form of albumose, 

 which is therefore found in some extracts. Finally, the phos- 

 phates and other inorganic salts, being largely soluble, pass 

 into the extract and constitute a considerable part of the fin- 

 ished pasty product. 



In this country " extract " is made by concentrating the 

 broth resulting from the boiling of beef as a step in the can- 

 ning process. Large quantities of meat being boiled in the 

 same water, it becomes rich in the " extractives " and is finally 

 boiled down to the usual pasty condition. Before the concen- 

 tration is complete the liquid is filtered and skimmed and 

 therefore leaves a residue free from fat or fiber. Roughly 

 speaking the paste extract has about this composition : 



Water 20 



Salts 20 



Organic substances 60 



Numerous analyses have been made of some of the commer- 

 cial extracts, but the methods employed have not always been 

 delicate enough to furnish trustworthy information. This is 

 especially true as regards the amounts of so-called peptone 

 and albumose present, for which the definitions have not been 

 fairly uniform until comparatively recently. The recognized 

 relations of these substances are explained in the chapter on 

 protein compounds. Analyses made by the older methods 



