tion does not help the curdling by rennet, but that the presence of a soluble calcium salt is necessary; it is immaterial whether the salt is phosphate or chloride, etc. According to Mayer (Milchzeitung, x, 36), when milk is heated at 75° it undergoes a change, and at a still higher temperature, but still much below 100°, it loses its power of being curdled. Experiments made by the author show that milk does not necessarily quite lose the power of being curdled by being heated at 100°, although the time required to curdle milk so treated is much lengthened, especially with milk of less than the usual acidity. The reason that boiled milk will either not curdle at all, or requires a longer time to curdle than fresh milk, is that a part of the dissolved calcium salt is precipitated as tricalcium phosphate. For the same reason curdling of milk by rennet is also prevented, or retarded, by adding more or less alkali. In either case, the property of being curdled by rennet may be restored to the milk by adding acid, passing carbonic anhydride through it, or by the addition of a soluble calcium salt. The author confirms. Schaffer's statement that boiled milk treated with carbonic anhydride curdles more quickly than fresh milk. ON THE ACID FERMENTATION OF MILK.1 BY DR. FOKKER. It has been well known for some time that the souring of milk is caused by bacteria, and one would expect that by this time the specific germ would be sufficiently well known. But it is not so. Hueppe and Marpmann, who have studied the subject minutely, are of opinion that there are more germs than one that possess the power of souring milk, and Grotenfeld has quite recently declared that the milk-souring germ is a modification of ordinary saprophytes, or that its properties are due to culture, and that there is no specific germ ferment causing the acid fermentation of milk. Our author has spent some considerable time in experimenting on the subject, and his paper consists of a short description of these experiments, and a resume of the conclusions he draws from them. He agrees with Grotenfeld, and thinks his own experiments justify him in maintaining that the rôle played by the germ in milk souring is a 1 Fortschritte der Medicin, June 1st, 1889; translated by W. A. Stewart for the Medical Chronicle, July. , 1889 . Jour. Pharm very subsidiary one. For his experiments he first takes four small retorts (Kölbchen) containing each 50 ccm. of sterilized milk, and adds to them different quantities of a pure culture of the so-called milk ferment germ, e. g. :— This experiment was repeated several times, always with a similar result. The natural conclusion is that the fermentation is influenced by something besides the germs. Might it be the casein? Before Pasteur discovered the germs Liebig held that casein was the specific milk ferment, and the following experiment supports Liebig : The next experiment with casein added is still more striking: This proves that the amount of casein has considerable influence; still, the fermentation is not in proportion to the amounts of casein added. This, however, is explained by the increased concentration of the fluid, as a parallel experiment, with fresh milk (infected with sour) and milk sugar, proves :— The casein evidently plays a part—an important part, but what part? Liebig maintained that casein was itself the ferment, but Pasteur proved the germs indispensable. Pasteur's mistake lay in considering the casein only a food for the germs. What is our author's opinion? He holds, as he explained two years ago, that animal protoplasm, as blood, muscle, etc., has the power, without the aid of germs, of turning starch into sugar and sugar into acid; casein resembles animal protoplasm in this respect, and consequently in the souring of milk two factors are at work, one acid fermentation being due to the casein and another to the germs. If this be true, the place of the casein might be taken by other substances. He finds that it is so. Coagulated albumen and yoke of egg have a particularly powerful action. He found also that heating the casein for one and one-quarter hours (in steam of five atmospheres pressure) had no effect in diminishing, but even increased its power as a ferment. Is the action then purely mechanical, depending like that of platinum sponge on porosity? It seems not. Wadding and amber have no effect; glass-wool, by giving alkali to the fluid, even diminishes its acidity. Sponge slightly increases it, owing to its animal basis. One may conclude then that this "power of furthering the production of acid" is peculiar to animal substances. The method of action we do not know and vital (Wirkungen der Lebenserscheinungen) is the adjective Fokker would apply to it, life, however, being always considered resolvable into simple chemical action. What part do the bacteria take? Fermentation, we know, is impossible without them. The germ, as he poetically puts it, is the spark that kindles the firework— that it turns out a pillar or a temple, depends not on the spark, but on the construction of the firework; and, as a spark from another fire or a spark from a match box begins it equally well, so also, according to Grotenfeld, the fermentation may be set agoing by the regulation germ, or by an ordinary saprophyte a little bit modified. Our author is by and bye to give us the result of further researches on the subject. He has found in the atmosphere about a goat and on the hairs of the same animal bacteria capable of souring sterilized milk. He found numerous others, but none capable of curding and acidifying to the same extent or with the same rapidity as the germ in ordinary sour milk. Jour. Pharm , 1889 ON THE ESTIMATION OF DIASTASE IN MALT EXTRACT. BY A. PERCY SMITH, F. C. S. The method usually recommended for the estimation of diastase in wort or extract of malt depends for its results upon the time taken to saccharify a known weight of starch, the end of the reaction being ascertained by the failure of iodine to strike a blue color. This method is, in my opinion, defective and inaccurate. A nondiastasic extract cannot be distinguished from one which contains a small quantity only of the ferment without the employment of an elaborate system, using starch solutions of many and varying strengths. The end reaction is not sharp, owing to the starch being reduced to a minimum and to the solution being hot. A more convenient and exact method, although not claiming scientific accuracy, consists in estimating the reducing-power of the extract on Fehling's solution before and after digestion with an excess of starch during a period of four hours at a temperature of 60° C. The starch solution I employ has a specific gravity of about 1·02, and is made by dissolving a dessertspoonful of starch in about two litres of water, using the supernatant fluid after deposition has taken place. The actual strength is of no consequence. In the examination of thick malt extracts I make a 1 per cent. solution in distilled water, taking care not to heat it above 60°C. in the act of solution; 10 cc. of this are diluted with 150 cc. of water and boiled in a dish, while the Fehling is added from a burette held in the hand. I prefer this method to the converse, as it is easier to determine the presence than the absence of a blue tint. The operation is more rapid, and one avoids the discrepancy caused when invert sugar acts upon a larger quantity of copper solution than it is able to reduce. In a duplicate experiment in which the copper solution is added all at once, instead of gradually, it will be found that cc. less is required. The same quantity of solution, viz. 10 cc., is digested with 25 cc. starch solution for four hours at 60° C., when it is diluted with 150 cc. water and treated as above. The number of cc. of Fehling used in each case is calculated into "sugar" per cent., and their difference into "increase per cent." Less than four hours' digestion with starch will not suffice, although the chief part of the work is done during the first hour. Thus the following numbers show the results of a series of experiments embracing a period of four hours, and give the number of cc. of Fehling taken by 5 cc. of a 1 per cent. solution of extract of malt. Time... hour 1 hour 1 hour 2 hours 11.5 12 12.5 3 hours 4 hours 13 13.5 A longer time than four hours has not, in my experience, been found necessary. In dealing with wort make a 5 per cent. by volume solution, and proceed as above.-The Chemist and Druggist, June 29, p. 873. THE PRINCIPLE OF DISINFECTION IN MEDICINE.1 BY DR. CARTER. Dr. Carter's object is to indicate the dawn of new methods of treatment by which the destruction of infection, hitherto only practiced outside the body, is to be transferred to the tissues—a proceeding which he fitly calls disinfection. "As an indication of the kind of work that can be done in this direction, it is only necessary to allude to some suggestive experiments by Brieger, who found that the typhoid bacillus, although it grew well in peptone, appeared to form no alkaloids from it. When he cultivated it in beef-tea, however, he obtained as a product of decomposition an exceedingly small quantity of ptomaine, which among other effects, caused, when injected into guinea-pigs, profuse diarrhoea. The bacilli were not killed by the peptone, they were not even prevented from growing and increasing; but they were rendered powerless for evil. Should not a single fact of this kind afford a powerful stimulus to renewed study of the relations of diet to some kinds of disease?" "How new and how strange this is may be judged by the following quotation from Dr. Lauder Brunton's book on the 'Disorders of Digestion,' which was not published till 1886. 'One author,' he says, not even mentioning his name, 'has gone so far as to consider that the immunity which one attack of an infective disease confers against a subsequent one is due to alteration in the body, not by bacteria or other low organisms, but by a chemical substance which they produce, 1 Liverpool Medico-Chirurgical Journal; reprinted from The Medical Chronicle, June, 1889. 4 |