362 THE POPULAR SCIENCE MONTHLY. 



sheath or cell-membrane. It is evident that the loose or free juices 

 will be extracted by simple di£fusion ; those enveloped in membranes 

 by exosmosis through the membrane. The result must be the same in 

 both cases : the meat will be permeated by the water, and the sur- 

 rounding water will be permeated by the juices that originally existed 

 within the meat. As the rate of diffusion — other conditions being 

 equal — is proportionate to the extent of the surfaces of the diverse 

 liquids that are exposed to each other, and, as the rate of osmosis is 

 similarly proportioned to the exposure of membrane, it is evident that 

 the cutting-up of the meat will assist the extraction of its juices by the 

 creation of fresh surfaces ; hence the well-known advantage of minc- 

 ing in the making of beef -tea. 



It is interesting to observe the condition of lean meat that has thus 

 been minced and exposed for a few hours to these actions by immer- 

 sion in cold water. On removing and straining such minced meat it 

 will be found to have lost its color, and if it is now cooked it is insipid, 

 and even nauseous if eaten in any quantity. It has been given to dogs 

 and cats and pigs ; these, after eating a little, refuse to take more, 

 and, when supplied with this juiceless meat alone, they languish, be- 

 come emaciated, and die of starvation if the experiment is continued. 

 Experiments of this kind contributed to the fallacious conclusions de- 

 scribed in No. 6 of this series. Although the meat from which the 

 juices are thus completely extracted is quite worthless alone, and meat 

 from which they are partially extracted is nearly worthless alone^ 

 either of them becomes valuable when eaten with the juices. The 

 stewed beef of the Frenchman would deserve the contempt bestowed 

 upon it by the prejudiced Englishman if it were eaten as the English- 

 man eats his roast beef ; but when preceded by a potage containing 

 the juices of the beef it is quite as nutritious as if roasted, and more 

 easily digested. 



Graham found that increase of temperature increased the rate of 

 diffusion of liquids, and in accordance with this the extraction of the 

 juices of meat is effected more rapidly by warm than by cold water, 

 but there is a limit to this advantage, as will be easily understood by 

 referring back to No. 3, in which are described the conditions of coagu- 

 lation of one of these juices — viz., the albumen, which at the tem- 

 perature of 134° Fahr. begins to show signs of losing its fluidity ; at 

 160° becomes a semi-opaque jelly ; and at the boiling-point of water 

 is a rather tough solid, which, if kept at this temperature, shrinks, and 

 becomes harder and harder, tougher and tougher, till it attains a con- 

 sistence comparable to that of horn tempered with gutta-percha. 



I have spoken of beef -tea, or Extractum Carnis (Liebig's Extract 

 of Meat), as an extreme case of extracting the juices of meat, and 

 must now explain the difference between this and the juices of an or- 

 dinary stew. Supposing the juices of the meat to be extracted by 

 maceration in cold water, and the broth thus obtained to be heated in 



