MECHANICS AND USEFUL ARTS. 93 



this residue, together with the bones of the slaughtered beasts, 

 be applied to our fields as manure, the farmer will be enabled to 

 produce a corresponding quantity of allniminous principles, and 

 to better supply our towns with them, eilhtn- in the shape of corn 

 or of meat and milk. ]\Iade into a marketable state, it may here- 

 after replace the Peruvian guano, Avhich very soon will disappear 

 from the market. 



" On the value of extract of meat as a medicinal substance, it 

 is unnecessary to say a word, it being identical with beef-tea, 

 about the usefulness and efficacy of which Opinions do not differ. 

 At the same time, I may remark that it is a mistake to think that 

 beef-tea contains any albumen, that there ought to be any gela- 

 tine or droits of fat to swim on its surface. Beef-tea does not 

 contain any albumen, and, if rightly prepared, ought to be free 

 from gelatine (or glue), whilst the supernatant drops of fat form 

 a non-essential, and, for many, an unwelcome addition. 



" I should be glad if these lines could assist in clearing up pub- 

 lic opinion on the value of exti-act of meat as a nutriment ; my 

 aim being, on the one hand, to reduce to their right limit hopes 

 too sanguine ; on the other, to point out the true share which the 

 extract of meat can have in the nutrition of the people of Europe. 

 In doing this, I know full well that whatever may be said for its 

 recommendation would be in vain, if the extract of meat did not 

 supply a public and generally felt necessity, and if it could not 

 stand the test of our natural instinct, — a judge not to be bribed. 

 *' I am, sir, your obedient servant, 



"Justus Liebig. 



"Munich, November, 1865." 



In a letter to the "London Journal of Pharmacy," written by 

 Liebig, the following remarks occur: — 



" It has been observed that the color and taste of the Fray Ben- 

 tos Extract vary ; this is owing to the difference of sex and. age 

 of the animals. ° 



" The meat of oxen always yields an extract of darker color 

 and stronger flavor, reminding somewhat of the flavor of fresh 

 venison — pleasant when diluted. The extract of cows' meat is 

 of lighter color, and a mild fla\'or, and is preferred by many per-_ 

 sons. The meat of animals under four years cannot be used for' 

 the manufacture of extract ; it yields a pappy extract of weak 

 taste, like veal, and without flavor. 



" According to the predominance of ox or cows' meat, the color 

 and taste of extract varies, which is by no means a fault of the 

 manufacturing process, and is fully explained by the preceding 

 remarks. The extract of ox meat is, however, richer in creatinin 

 and sarcin than the cows' meat extract. 



"It is extremely difficult, as regards extracts of meat, — the 

 genuineness and purity of which are not discoverable by the eye, 

 — to protect the puljlic against fraud. All manufacturers prepare 

 their extract according to what they call ' Liebig's process ; ' but 

 since I have given only general, and not special, directions for 

 manufacture, it so happens that every one fiJls in the details after 



