ARTIFICIAL DIGESTION. 549 



cently killed sheep, calf, ox, or pig, especially if the animal be slaugh- 

 tered whilst digestion is going on in the stomach. Finely cut portions, 

 or scrapings of the mucous membrane, are to be macerated in 20 times 

 their weight of cold water for 24 hours, with frequent agitation of the 

 mixture. A temperature as low as 50 is desirable, to prevent the 

 pepsin, extracted from the membrane, from exhausting itself, more or 

 less, in the digestion of that membrane itself. The fragments of the 

 mucous membrane being allowed to subside, the supernatant fluid is 

 poured off, forming a solution of pepsin extracted from the peptic cells, 

 but containing only a slight and insufficient quantity of free acid; for 

 the pepsin is stored up in the peptic cells, so that it may be extracted 

 by water after death, whilst the acid of the gastric juice is probably 

 secreted only when required, perhaps by the columnar epithelial cells; 

 it therefore ceases on the death of the animal. Hence the solution of 

 pepsin as above prepared, requires an addition of hydrochloric acid 

 to make it digest actively. Too little, or too much, acid diminishes its 

 peptic properties. Ten minims, i. e., about 13 drops of the pure hydro- 

 chloric acid of commerce, to every ounce of the digestive fluid, is said 

 to be the best proportion. 



The inefficiency of the acid, and of the solution of pepsin, separately 

 employed, and the powerful effect of the two together, may be thus 

 strikingly illustrated. Three fluids are to be prepared, one, of hydro- 

 chloric acid and water, in the proportion of 13 drops to the ounce; a 

 second, of the above described solution of pepsin, exactly neutralized 

 by carbonate of soda; and a third, of the same solution, acidified with 

 hydrochloric acid, in the proper proportions. In equal quantities of 

 these fluids contained in glass jars of the same size, are suspended the 

 legs of fowls, or the fore-limbs of rabbits, either cooked or uncooked, 

 one in each jar; the jars are then placed in a water-bath, and main- 

 tained at a temperature ranging between 96 and 102, for 24 hours. 

 At the end of that period, the limb suspended in the hydrochloric acid 

 and water, is found to be slightly swollen, pale and semi-transparent, 

 whilst the solution, itself of a yellowish-tint, is quite clear, and free 

 from deposit. The limb submitted to the action of the neutralized 

 solution of pepsin, which is itself slightly turbid, appears sodden, but 

 its surface is nowhere dissolved ; the fluid itself is darker, but not more 

 turbid. In the acid solution of pepsin, however, all the soft parts of 

 the digested limb are, as it were, eaten away and pulpified, or dissolved ; 

 the tendons disappear first, then the muscles, next the ligaments, and 

 lastly, even the bones and cartilages are more or less attacked, the 

 slight residual mass contrasting strongly with the undissolved and 

 swollen limbs in the other two solutions; moreover the fluid itself has 

 a brownish color, and presents a soft flocculent or pulpy grumous sedi- 

 ment, several inches deep, which, on the slightest agitation, mixes 

 easily with the fluid above, and resembles the digested contents of the 

 stomach, after taking animal food. 



Phosphoric, sulphuric, and even nitric acid may be employed in the 

 artificial digestive fluid, but they are not so suitable as hydrochloric. 

 Very strong acids, metallic salts, caustic alkalies, alum, tannin, and 

 strong alcohol, destroy its digestive properties, and so does a tempera- 



