BY OUR BERLIN CORRESPONDENT. In hardly any branch of medicine have theoretical results found such rapid and successful practical uti lization as in bacteriology. Within a few decades bac teriology has been developed to a science which even specialists have some difficulty in covering in its totality. This rapid growth is easily understood, for the very aim of this doctrine is to free humanity from its most terrible foes, infectious diseases. Among its most important achievements are doubt less the introduction of antisepsis in surgical practice and the discovery of the diphtheria serum by Von Behring. Prof, von Behring in 1892 found that animals treated with virulent diphtheria cultures generate in their blood serum some protective substance or anti-toxin. Apart from protecting the animals themselves this anti toxin will render other subjects immune from diphtheria toxin or infection by diphtheria microbes. The most important point of Prof, von Behring's work in con junction with Kitasato and Wer nicke, however, consisted in demonstrating that the serum, apart from its protective virtue, possessed curative qualities. An extension of the experience gained in connection with animal experiments to human practice was, however, far from being as easy as would appear at first sight. In fact, the percentage of anti-toxin in the serum of im mune animals had to be increas ed sufficiently to allow therapeu tical effects to be obtained on diphtheritic patients by vaccina tion with small amounts of a serum. Furthermore, owing to the frequency of diphtheria, means had to be provided for permanently producing the therapeutical serum in large quantities. Extensive institutes were set apart for its production and the analyzing of its composition. The same institutes further had to deal with the problem of extending to other diseases the ideas which had proved so fertile in connection with diphtheria and tetanus. Owing, however, to the diffi dence at that time produced by the disappointing re sults of Koch's tuberculine, much difficulty was experi enced in obtaining the necessary funds. One of the first and most important serum insti tutes is the Vienna Institute, founded by Prof. Pal-tauf with funds provided in part by the Austrian gov ernment and partly by an anonymous benefactor. In addition to supplying the whole amount of diphtheria serum con sumed in Austria, this institute is engaged in general research work on sero-therapeutics. Horses are at present used ex clusively for yielding serum, and these are mostly young horses (four to eight years old) which should be perfectly healthy, though foot defects would not prove an objection. These animals are housed in large, light, and well-ventilated stables, the floor, walls, mangers, etc., of which are of washable material and are kept scrupulously clean. Care is taken in the feeding of the animals as well as in insuring cleanliness and frequent exercise in the open air. These horses are rendered im mune by a subcutaneous injection of diphtheria virus close to the neck, using every precaution to warrant a perfect antisepsis. A graduated calibrated cylindrical vessel, the lower end of which is connected through a piece of rub ber tubing with a needle that is thrown under the skin of the animal, is used to make the injection. Its upper end connects with a rubber pump. The horses will react to the injection of toxin with both local symptoms (swelling of the vaccinated parts) and general symptoms (fever, depression, di minution of appetite, etc.), but after one or two days normal conditions will be re-established. In the case of excessive doses, especially at the beginning of a treatment, dangerous phenomena and even death may occur. Owing to their increasing immunity, the ani mals, which are vaccinated on an average every four or five days, will eventually stand enormous quanti ties. In fact, while a few drops of a violent virus may prove fatal with a first inoculation, a quart will afterward fail to exert any strong reaction. After two to three months the treatment will be finished, and the horses may now be used for producing thera peutical serum. But in many cases a horse will form only small quantities of antitoxin, and the sera of such animals will be useless, enormous quantities be ing required for obtaining curative effects. The first thing to be done is therefore to ascertain whether a given animal will yield antitoxin, which can only be done by practical test; if not, it should be used for other purposes. Serum institutes are therefore compelled to keep larger numbers of ani mals than would be necessary for supplying the re quired quantities of serum. In many cases a horse supplying no diphtheria serum will be suitable for yielding other protective substances. The blood of the animals is derived by bleeding, the jugular vein at the neck being compressed with a pelotte, and a sterile trocar being thrown into the vein. The trocar is connected through a rubber tubing with big sterile glass vessels, in which the blood is allowed to ac cumulate. Six liters (about six quarts) of blood are generally derived, after which the compression and subsequently the trocar are removed, when the small wound will heal after a few days. The vessels filled with blood are placed in special cooling compart ments, in which, owing to coagulation, the blood will be separated into the black-red clot of blood, which will sink to the bottom, and the clear gold-yellow serum, which remains at the top. Each 6 quarts of blood will yield an amount of serum varying between ll/2 and 2.1 quarts. After twenty-four hours the serum is removed by means of syphons from the clot of blood, and after standing a few days, is tested as to its sterility and efficiency by animal experiments, and is then filled into small flasks, in which it is sold. All these manipulations require an enormous amount of care and accuracy, as well as considerable technical skill. Working with serum is complicated considerably by the necessity of avoiding any patho logical impurities, lest the whole serum fraction be de stroyed by putrefaction. Any germ falling from the air into the serum, any contact with the hands or any non-sterile vessels or instruments, will involve this danger. In connection with the diphtheria serum, however, the resistance of the liquid can be increased by an addition of 0.5 per cent of carbolic acid, while in that of other sera an absolute absence of germs is the only guarantee of preservation. In addition to diphtheria serum there are produced at the Vienna Institute some other therapeutical sera including an anti-dysentery serum. Dr. Kraus and Dr. Doerr conceived the idea that it should be pos sible to obtain antitoxins in the case of other infec tious diseases, provided the microbe in question be isolated in an artificial manner. A solution of this difficult problem was found in the case of dysentery microbes. No obstacle was encountered in rendering horses immune with dysentery toxin and testing the efficiency of th serum, first on a sensitive animal and next on man. The first tests were made on soldiers. Patients who lay in their beds with pale cheeks, sunken eyes, and hardly noticeable pulse would frequently recover in a few hours after a single injection. Those patients who for the sake of comparison had not received any injection urgently asked for the treatment, which before their eyes had wrought such surprising improve ment in the condition of their comrades. In the case of typhus and cholera there also seems to be some chance of developing suc cessful sero-therapeutical meth ods, and in connection with the laborious work carried out in this direction, the Vienna Institute has a considerable share. Minimum amounts of these sera will by timely injection pre vent the outbreak of infectious disease, as has been shown by ex periment and statistics; and this adds greatly to the wide usefulness of these institutes. Two Eggs a Day from a Hen. In a recent issue of Science, Prof. Gilman A. Drew, who has been conducting experiments in connection with the egg-laying possibilities of hens at the Maine Experiment Station, quotes instances of hens which have laid two eggs within twenty-four hours. The most interesting case is that of a pullet, which apparently laid two eggs in one day early in March, 1906. During March and April there are records of five days on each of which this hen laid two eggs. Although she was carefuUy watched for more than a year And a half, there are no other records of her having laid more than one egg in a day. It should be added that the records of days on which she was known to lay two eggs came during the months of her greatest egg-producing ac tivity. Prof. Drew has noted a num ber of instances of hens laying two eggs in a day, but the rec ords show that in most cases on either the day before or the day after that on which two eggs were deposited no egg was laid. Such cases may reasonably be accounted for by supposing pre mature or delayed delivery, but this cannot be true of the hen whose record has been given, where, for the five days begin ning with April 3 and ending with April 7, eight eggs were laid. There are two other instances where an average of more than one egg in a day for a limited period was made. In both of these cases the possible mistake in the reading of the numbers on the distinguishing bands by which the hens are identified is to be considered. There are eight other instances recorded where hens laid two eggs in a day, but in all of these cases on either the day previous or succeeding the day on which two eggs were laid no egg was laid. More interesting than these abnormal occurrences is the report of hens which at the station have laid 255 eggs within twelve months. Cleaning Objects of Aluminium.—To restore luster to tarnished aluminium it is sufficient to immerse it in water slightly acidulated with sulphuric acid. To small articles of aluminium a soft brush may be ap plied. For the bath, water with a little carbonate Of soda will suffice.