Lactic acid

“ Lactic acid may be given in doses of one or two teaspoonfuls, similarly diluted. It has been asserted, on theoretical grounds, that lactic acid and the lactate of sodium are directly hypnotic, but its experimental use has never given satisfactory results. Phosphoric acid has been used in the same way, with very similar effects. An impure solution of phosphoric acid, known as Horsford’s Acid Phosphate, has been extensively used for its supposed hypnotic properties. It assists digestion, stimulates the kidneys, and by its general diffusion promotes molecular activity throughout the body. ”

“ Under the influence of lactic fermentation, sugar and starch are converted into lactic acid. When it has once begun, it develops rapidly, and soon decomposes a large quantity of glucose; but as it can proceed only in a neutral liquor, the presence of the acid itself speedily checks its own formation. Then, however, another ferment is liable to act upon the lactic acid already formed, converting it into butyric acid, which is easily recognized by its odor of rank butter. ”

“ In dogs taking a meat diet and excreting urine characterized by abundant indican and high ethereal sulphates there was no falling off in putrefaction as a result of administering doses of lactic acid as large as five grams daily. It seems to me doubtful if under these circumstances enough lactic acid could reach the large intestine to exert even a moderate anti-putrefactive action. The experiments just mentioned represent an extreme case, since they were made on animals living exclusively on meat. The results obtained can not, therefore, be regarded as strictly applicable to man. ”

“ It includes not only the true lactic acid types in which no gas is formed, but those species capable of producing gases and various kinds of acids. These organisms are the distinctively milk bacteria, although they do not predominate when the milk is first drawn. Their adaptation to this medium is normally shown, however, by this extremely rapid growth, in which they soon gain the ascendency over all other species present. It is to this lactic acid class that the favorable flavor-producing organisms belong which are concerned in butter-making. They are also indispensable in cheese-making. ”

“ It appears, therefore, that inactive lactic acid can be quite readily obtained in large proportion from the sugars by the action of alkalis, whilst alcohol can only be prepared in comparatively small amount and probably only as a secondary product of the decomposition of lactic acid. ”

“ This organism is a powerful lactic acid ferment, forming large amounts of lactic acid from milk sugar while forming very little alcohol. The organism grows well in milk and on some media containing an abundance of soluble carbohydrates, as, for instance, in malt extracts. We may take the behavior of B. bulgaricus in the digestive tract as being typical of efficient lactic acid bacilli in general. There are two questions which we must put to ourselves regarding the therapeutic effects of such bacteria. ”

“ It is a real putrefaction of the lactic acid which has taken place, but a putrefaction without putridity, for the lactic acid contains neither sulphur nor phosphorus, those elements of offensive gaseous combinations which are deleterious for man but inoffensive for vibrios. No, I am wrong: putridity shows itself, but in so slight a degree that it is almost inappreciable. ”

“ Besides the production of carbon dioxide during decomposition, a certain portion of milk sugar is converted into lactic acid, some of the casein and albumen are broken up into simpler constituents, and a small proportion of alcohol produced, which by oxidation appears as acetic acid, while the fat is in part separated into free fatty acids, which ultimately unite with the ammonia produced by the breaking up of the albuminoids. The main fermentation of milk is a special kind which of late years has been much studied, and is known as lactic fermentation. ”

“ The filtrate is then concentrated to a syrup by evaporation, and agitated in a test-tube with a mixture of 1 part each of sulphuric acid, alcohol, and water, and 10 parts of ether. After standing at rest for some time, the ethereal solution is separated by means of a pipette and evaporated to dryness in a tared capsule. The residue (impure lactic acid) can be weighed, or it is dissolved in [147] water, the solution treated with zinc carbonate, and the lactic acid determined as zinc lactate, which contains 54·5 per cent. of the anhydrous acid. ”

“ It must be remembered that no food is usually taken in fever; this would at length quite cut off the usual source of this lactic acid, which is the starch and sugar of the food, and render it necessary that the animal tissues should continue to undergo oxidation, to maintain the animal heat. Now if we compare the commonly received formula of Proteine with those of Lactic acid and Tartaric acid, it will at once be seen, as was pointed out some time ago by Dr. Murray, that the latter contain more Oxygen, in proportion to their Carbon and Hydrogen, than is found in Proteine, or Albumen. ”

“ Lactic acid is in fairly common use as a deliming agent. In practice 1 per cent. lactic acid (50 per cent. strength) calculated on the wet weight of pelt, is used, added gradually in small quantities. This does not remove the whole of the lime, but sufficient for the skins to puer quickly.
Some tanners measure their acid per dozen skins. In a case which came under my notice, 1200 c.c. 90 per cent. formic acid were being used for ten dozens medium goat skins at a temperature of 35° C., time 1 1/4 hours. ”

“ This acid is ascribed by some to Urate of Ammonia, which is to a small extent soluble in water. Others consider that it is due both to this and to Phosphoric acid, which is the opinion of Dr. Prout and Dr. G. Bird. Others attribute it to Lactic acid, which is stated by Berzelius, Lehmann, and Simon, to exist in healthy urine. Some consider the acid to consist in a Super-phosphate of Soda. Liebig supposes that it is due to Uric acid, held in solution by the common Phosphate of Soda. He also considers Hippuric acid to be an invariable ingredient in healthy human urine. ”

“ It seems to have a bleaching effect, and from a nutritive point of view comes very near to new milk. Again, the proteids of the milk and mineral matter are practically digested by the action of the lactic organisms, and new milk undergoes no change during fermentation in the dough. The changed condition in the buttermilk is of great advantage, and lactic acid adds flavor to bread made with compressed yeast. There is no reason to suppose that bread made with buttermilk will go sour sooner than that made with fresh milk if the fermentation is [158] managed properly. ”

“ And lactic acid, with from five to twenty parts of water; and an [Pg 151] ointment containing a drachm each of bismuth subnitrate and white precipitate to the ounce. Hydrogen peroxide occasionally acts well. Trichloracetic acid, usually weakened with one or two parts water, may be cautiously tried. The application of a strong alcoholic solution of resorcin, twenty to fifty per cent. strength, is also valuable, as is also a two to ten per cent. ”

“ It does not liquefy gelatine. It grows best at blood-heat; but much above that it fails to produce its fermentation, and it ceases to grow under 10° C. It inverts milk-sugar and changes it to dextrose, from which it then produces lactic acid. Sugars do, however, differ considerably in the degrees to which they respond to the influence of the lactic ferment, and some which are readily changed by the alcoholic ferment are untouched by the Bacillus acidi lactici. It will be necessary to refer again to this micro-organism when we come to speak of milk and other dairy products. ”

“ Bacillus lacticus (Bacterium acidi lactici, Zopf) is always found in milk which has stood for some time, and in sour foods (cabbage, cucumbers, etc.) ; it turns the milk sour by producing lactic acid fermentation in the sugar contained in the milk; the lactic acid formed, eventually causes the coagulation of the casein. It resembles the Vinegar-bacteria, occurring as small cylindrical cells, rarely in short rows; not self-motile.—Several other Bacteria appear to act in the same way, some occurring in the mouth of human beings; some of these Bacteria give to butter its taste and flavour. ”

“ Lactic acid is the most copious product thrown out in the disease called rheumatic fever, and, as many of the phenomena resulting from that disease take the same form and character as those producible by lactic acid, I infer from the best evidence attainable that this acid, the product of a fermentative change going on in the body during acute rheumatism, is the cause of the secondary structural affections which so frequently follow acute rheumatism. ”

“ Further, many kinds of wine have a somewhat acid taste. In Russia, kwas, especially in the acid form, is consumed in great quantities. Moreover, acid fruits and green vegetables are used as food, and they are either of themselves acid, or made so in the preparation. In medicine this instinct is likewise often made use of, and acid solutions, especially of hydrochloric and phosphoric acids, are prescribed in digestive disturbances. Finally, Nature itself constantly endeavours to prepare lactic acid in the stomach in addition to the hydrochloric acid. ”

“ Where the stomach secretes no free hydrochloric acid it is reasonable to suppose that the use of lactic acid in weak concentration exerts some anti-fermentative action, especially against such microorganisms as do not readily grow in acid medium. ”

“ A maker who can preceive it only as it is revealed by stringing on the iron is not competent to be in charge of a factory, for anybody could detect it there. The development of lactic acid is a species of fermentation induced by the spontaneous increase of inherent minute bacteria. It takes the same experience to perceive and govern it in milk and cheese as it does practice with square and compass to become a carpenter. We cannot tell you all about it—it will take many days of careful observation and fine testing to understand its nature enough to make it your servant in the cheese making art. ”

“ This organism has the power of transforming milk sugar and other saccharoses into lactic acid, with evolution of carbonic acid gas. It is rarely found in the saliva or mucilage of the teeth. In these are two micrococci, both of which cause the production of lactic acid, but which manifest differences in their development under cultivation. There are also two pigment forming bacteria, Micrococcus prodigiosus, which produces intensely red spots, and the yellow micrococcus of osteomyelitis. ”

“ Unsaturated compounds generally show larger rotative powers; amyl alcohol with −5° produces an aldehyde with 15 ; succinic (diamyl) ether with −9° produces fumaric ether with 15°, &c. Cyclic configuration especially leads to the highest values known: the lactic acid with 3 leads to a lactone with −86°,
H3C-CH-COO
I I
OOC-HC-CH 3 ;
mannosaccharic acid, H0 2 C (CHOH) 4CO 2 H, to a dilactone (with two rings, formed by the loss of two molecules of water) with 202°, whereas the original acid only shows a small rotation. ”

“ Nor is there sufficient reason for supposing that the amyloid substance of the liver is transformed into sugar, for this substance is as readily oxidizable and as fit for force fuel as sugar. Nay, it may be questioned whether sugar itself is the force-fuel which the system is in need of. There is a very rapid generation of lactic acid in the stomach and bowels when sugar is taken as food, and it is not unintelligible that it should be so; for, with the help of a ferment of some sort, grape-sugar is readily converted into lactic acid. ”

“ It has been clearly proved that the microbes which produce lactic acid can, and do, control the growth of other microbes within the body, and that the lactic microbe is so much at home in the human body that it is to be found there several weeks after it has been swallowed. ”

“ It is important to avoid a strong solution and local excess, hence lactic acid must be added gradually so that the liquor is never stronger than 0.2 per cent. Drumming and paddling is an advantage in deliming.
The tannage is light in most cases, partly because some of the finished goods are sold by area, but partly also because even if sold by weight, the weight is obtained quicker and more easily by stuffing, which course is also often preferable to obtain the desired mellow feel, waterproofness and durability. Hence it is seldom that strong liquors are employed. ”

“ Bases, consisting of amines, skatol, and indol, and varying amounts of ammonia, according to the age of the dung.
The organic acids exist partly as salts of the alkaline earths, partly combined with amines. A distillation of “puer,” after acidifying with H2SO4, gave 2·2 grm. per litre of volatile acids reckoned as acetic. No HCl came over. On decomposing the sodium salts of the acids with H2SO4, the smell of butyric acid predominated. I have also shown the presence of lactic acid in the dung, but have been unable to determine the amount. ”

“ Now every animal is continually producing acids in its cells, especially carbonic acid and lactic acid. It probably produces also substances which could have the opposite effect and which decrease the heliotropic sensitiveness of the animals. ”

“ Metchnikoff's views as to the value of lactic acid have met with not only the legitimate skepticism and criticism of the medical profession, but also with the usual ridicule from the press. "Who would want to live one hundred and fifty years if he had to drink sour milk three times a day?" ”