Diseases of the Chest

easily differentiated from the BY normal contour and color of the A. R. MASTEN, M.D. s]dn Specific because without wheatridge, Colo. a pl.ece(]jng infection with tubercle bacilli no reaction will occur. Accurate because no other known combination of factors will give the same result. That is, a person cannot become sensitive to tuberculin by any means except a previous infection with tubercle bacilli. Since 1800 when Robert Koch first discovered tuberculin and noted its action, many methods of preforming the tuberculin test have been tried. The most, accurate, and therefore the most preferable, is the intracutaneous test proposed by Mantoux in 1907. By this method a small measured amount of tuberculin of known concentration is injected into the skin of the forearm producing a small weal at the point of injection. The test is most frequently performed by injecting O.I cc of a solution consisting of one part Old Tuberculin in 999 parts of normal salt solution. This dose contains 0.1 milligram of tuberculin and is a satisfactory amount for general purposes in the testing of children. Adults, on the other hand, usually react to a much smaller amount of tuberculin and should always be tested with a dose of 0.01 rag. to avoid excessive and unpleasant reactions. In order to obtain accurate information, all negative reactors must be relested with larger amounts of tuberculin. For children, the dosage is increased from 0.1 mg. to 1. ing., while with adults it is increased from 0.01 mg. to 0.1 ing. and then to 1. mg. When time is not an important factor it is usually advisable to make the first test with 0.01 mg. of tuberculin, even in the testing of children. In 1934 Long, Seibert, and Dorset perfected the material known as Purified Protein Derivative. This substance will, no doubt, soon displace Old Tuberculin THE TUBERCULIN test is a simple and effective method by which a person infected with tubercle bacilli can be distinguished from a person who has not been so infected. The present day emphasis on early diagnosis makes this test extremely valuable since it detects the presence of tuberculosis long before other means of examination have any value. The time has arrived," says Myers, "when tuberculin testing should be as much a part of every medical examination, regardless of the age of the patient, as the Wassermann or urinalysis tests are." In essence, the tuberculin test is a practical application of the complex tissue phenomenon known as allergy. Although the exact nature of allergy is still unknown, many of its actions are easily recognized. For example, it has been found that living tissue becomes sensitized or hypersensitive to foreign proteins, proteins differing from those of its own composition, causing a marked reaction to occur whenever the same protein is introduced a second time. Thus the tissues of a person infected with tubercle bacilli will show a definite and specific reaction when injected with the products of tubercle bacilli. Contrary-wise, a person who has never been infected with tubercle bacilli will show no reaction when injected with the same material. The tuberculin test is simply a visible application of the above mentioned tissue reaction. When tuberculin, a substance composed of the products of tubercle bacilli, is injected into the skin of a tuberculous person the area of injection becomes red, swollen, and slightly brownish by the end of forty-eight hours. A nontuberculous person, on the other hand, will show no reaction when injected with tuberculin. The tuberculin reaction is, therefore, definite, specific, and accurate. Definite because an area of redness with swelling and a brownish discoloration is culin tests. On the basis of three thousand as the standard material for making tuher-