OF BODIES DESTITUTE OF NITROGEN. 331 



heated to the temperature of boiling water in vessels 

 from which the air is completely excluded. Food 

 thus prepared has been kept for fifteen years, and 

 upon opening the vessels, after this long time, has 

 been found as fresh and well-flavoured as when origi- 

 nally placed in them.* 



The action of the oxygen in these processes of 

 decomposition is very simple ; it excites changes in 

 the composition of the azotized matters dissolved in 

 the juices, — the mode of combination of the elements 

 of those matters undergoes a disturbance and change 

 in consequence of their contact with oxygen. The 

 oxygen acts here in a similar manner to the friction 

 or motion which affects the mutual decomposition of 

 two salts, the crystallization of salts from their 

 solution, or the explosion of fulminating mercury. 

 It causes the state of rest to be converted into a 

 state of motion. 



When this condition of intestine motion is once 

 excited, the presence of oxygen is no longer neces- 

 sary. The smallest particle of an azotized body in 

 this act of decomposition exercises an influence upon 

 the particles in contact with it, and the state of 

 motion is thus propagated through the substance. 

 The air may now be completely excluded, but the 



* The process is as follows : Let the substance to be preserved be 

 first parboiled, or rather somewhat more, the bones of the meat being 

 previously removed. Put the meat into a tin cylinder, fill up the 

 vessel with seasoned rich soup, and then solder on the lid, pierced 

 with a small hole. When this has been done, let the tin vessel thus 

 prepared be placed in brine and heated to the boiling point, to com- 

 plete the cooking of the meat. The hole of the lid is now to be closed 

 by solderinor, whilst the air is rarefied. The vessel is then allowed to 

 cool, and from the diminution of volume, in consequence of the re- 

 duction of temperature, both ends of the cylinder are pressed inwards 

 and become concave. The tin cases, thus hermetically sealed, are ex- 

 posed in a test-chamber, for at least a month, to a temperature above 

 what they are ever likely to encounter; from 90° to 110° F. If the 

 process has failed, putrefaction takes place, and gas is evolved, which 

 will cause the ends of the case to bulge, so as to render them convex, 

 instead of concave. But the contents of those cases which stand the 

 test will infallibly keep perfectly sweet and good in any climate, and 

 for any number of years. If there be any taint about the meat when 

 put up, it inevitably ferments, and is detected in the proving process. 

 — Ure's Diet, of Arts and Manuf. 



