6i2 



FARMERS' REGISTER, 



[No. 11 



posed to putrefy than gelatine.* Acrordiiifr to 

 MM. Gay Lussac and Thenard, 100 parts offibrine 

 contain 



or carbon - - 53-360 



— oxygen - - 19-685 



— hydrogen - - 7 021 



— azote - - 19-934 

 Mucus is very analogous to vegetable gum in 



its character?; and as Dr. Bostock has slated, it may 

 be obtained by evaporating saliva. No experi- 

 ments have been made upon its analysis ; hut it is 

 probably similar to gum in composition. It is ca- 

 pable of undergoing putrefaction, but less rapidly 

 than fibrine. 



Animal fat and oils have not been accurately 

 analyzed; but there is great reason to suppose that 

 their composition is analogous to that of similar 

 substances from the vegetable kingdom. 



y/lhtmen has been already referred to, and its 

 analysis stated in the third lecture. 



Urea may be obtained by the evaporation of 

 human urine till it is of the consistence of a syrup, 

 and the action of alcohol on the cr\stallirie sub- 

 stance which forms when the evaporated matter 

 cools. In this way a solution of urea in alcohol is 

 procured, and the alcohol may be separated from 

 the urea by heat.f Urea is very soluble in water, 

 and is precipitated from water by diluted nitric 

 acid in the form of bright pearl-colored crystals; 

 this property distinguishes it irom all other animal 

 substances. 



According to Fourcroy and Vauquelin, 100 parts 

 of urea, when distilled, yield 



92027 parts of carbonate of ammonia. 

 4-608 carburetted hydrogen gas. 

 3-225 of charcoal. J 

 Urea, particularly when mixed with albumen or 

 gelatine, readily undergoes putrefaction. 



Uric acid, as has been shown by Dr. Egan, may 

 be obtained from human urine by pouring an acid 

 into it ; and it olien falls down from urine in the 

 form of brick-colored crystals. It consists of 

 carbon, hydrogen, oxygen, and azote; but iheir 

 proportions have not yet been determined. Uric 

 acid is one of the animal substances least liable to 

 undergo the process of putrefaction. § 



* Fibrine, especially of the blood, accordin{!j to my 

 experience, putrefies more readily than any other ani- 

 mal substance. In a few hours, at the temperature of 

 80° Fahrenheit, exposed to the air, by putrefacion it is 

 reduced from a solid to a liquid : the cnanpje is accom- 

 panied by a considerable disengagement of heat, and 

 formation of ammonia and carbonic acid. — J. D. 



t It is best obtained from the nitrate of urea, by 

 means of carbonate of potash and alcohol, according 

 to Dr. Prout's method. Pure urea is colorless, crys- 

 tallizes in four-sided prisms, and its solution in water 

 resists change for many weeks or even months. It is 

 the only animal compound (or proximate principle) 

 which hitherto has been formed artificially. — J. D. 

 { According to the analysis of Dr. Prout, it consists of 



Carbon - - - 12-24 



Nitrogen - - - 22-3 



Hydrogen - - - 4 



Oxygen - - - 16--J. D. 

 § It has lately been analysed by Liebig, and found 

 to consist of 



Carbon - - - 36-11 



Hydrogen - - - 2 34 



Nitrogen - - - 33-36 



Oxygen - - - 28-10 

 When pure, it is colorless, tasteless, and without 

 odor.— J. D. 



According to the different proportions of these 

 principles in animal compounds, so are the changes 

 they undergo different. When there is much sa- 

 line or earthy matter mixed or combined with them, 

 the progress of Iheir decomposition is less rapid 

 than when they are principally composed offibrine, 

 albumen, gelatine, or urea. 



The ammonia given ofTfrom animal compounds 

 in putrefaciion may be conceived to be formed at 

 the time of their decomposition by the combination 

 of hydrogen and azote; except this matter, the 

 other products of putrefaciion are analogous to 

 those afforded by the fe-mentaiion of vegetable 

 substances ; and the soluble substances formed 

 abound in the elements, which are the constituent 

 parts of vegetables, in carbon, hydrogen, and 

 oxyo-en. 



Whenever manures consist principall}' of matter 

 soluble in water, it is evident that iheir ferment- 

 ation or putrefaction should be prevented as much 

 as possible ; and the only cases in which these 

 processes can be useful are when the manure con- 

 sists principally of vegetable or animal fibre. The 

 circumstances necessary for the putrefaction of 

 animal substances are similar to those required for 

 the fermentation of vegetable substances : a tem- 

 perature above the freezing point ; the presence of 

 water, and the presence of oxygen, at least in the 

 first stage of the process. 



To prevent manures from decomposinsr, they 

 should bo, preserved dry, defended from the con- 

 tact of air, and kept as cool as possible. 



Salt and alcohol appear to owe their powers 

 of preserving animal and vegetable substances to 

 Iheir attraction for water, by which they prevent 

 its decomposinir action, and likewise to their ex- 

 cluding air. The use of ice in preserving animat 

 substances is owing to its keeping iheir tempera- 

 ture low. The efficacy of M. Apperi's method of 

 preserving animal and vegetable substances, an 

 account of which has been lately published, en- 

 tirely depends upon ihe exclusion of air. This 

 method is by filling a vessel of tin plate or glass 

 with the meat or vegetables; soldering or cement- 

 ing the top so as to render the vessel air tight ; 

 and then keeping it half immersed in a vessel of 

 boiling water for a sufficient time to render the 

 meat or vegetables proper lor food. In this last 

 process it is probable that the small quantity of 

 oxygen remaining in the ves.sel is absorbed ; for 

 on opening a tinned iron cannister which had been 

 filled with raw beef, and exposed to hot water the 

 day before, I found that the minute quantity of 

 elastic fluid which could be procured from it, was 

 a mixture of carbonic acid gas and azote. 



Where meat or vegetable food is to be preserved 

 on a large scale, for the use of the navy or army, 

 for instance, i am inclined to believe, that by 

 forcibly throwing a quantity of carbonic acid, hy- 

 drogen, or azote, into the vessel, by means of a 

 compressing pump, similar to that used for mak- 

 ing artificial Seltzer water, any change in the 

 substance would be more effectually prevented^ 

 No elastic fluid in this case would have room to 

 form by the decomposition of the meat; and the 

 tightness and strength of the vessel would be 

 proved by the process. No putrefaction or fer- 

 mentation can go on without the generation of 

 elastic fluid; and pressure would probably act with 

 as much eflicacy as cold in the preservation of ani- 

 mal or vegetable food. 



