In 401 cases of children under the age of two years, in which the serum treatment was used on the first and second day, the mortality rate was 11·8, in contrast with 39·7 where under similar conditions it was not used. Of 2,556 children between two and ten years of age, the death-rate was 4 per cent after antitoxin treatment, instead of 15·2 per cent in the other group.
Prof. Welch very truly and forcibly remarks: "The discovery of the healing serum is entirely the result of laboratory work. It is an outcome of the studies of immunity. In no sense was the discovery an accidental one. Every step leading to it can be traced, and every step was taken with a definite purpose and to solve a definite problem."
The importance of prompt treatment in this very fatal malady is shown by the following figures which we take from Prof. Welch's paper. The cases referred to were reported by nineteen different observers, and the total number treated was 1,489, with a mortality of 14·2 per cent. Of these cases, 222 were treated with the antitoxic serum on the first day of sickness, with a mortality of 2·2 per cent; 456 cases on the second day, with a mortality of 8·1 per cent; 311 on the third day, with a mortality of 13·5 per cent; 168 on the fourth day, with a mortality of 19 per cent; 116 on the fifth day, with a mortality of 29·3 per cent; 44 on the sixth day, with a mortality of 34·1 per cent; 104 after the sixth day, with a mortality of 33·7 per cent; 68 undetermined.
The time at my disposal will not permit me to dwell longer upon the practical results already attained in preventive medicine and in specific therapeutics as a result of bacteriological investigations. But before closing I desire to call attention, as briefly as possible, to the value of the recent additions to our knowledge relating to the causes of disease, in the way of an exact and early diagnosis. In certain infectious diseases such knowledge is of great importance, not only in the interest of the patient, but of others liable to infection. This is especially true in diphtheria and in tuberculosis of the lungs. In the first-mentioned disease an early differentiation of true diphtheria from pseudo-diphtheria is often impossible without resort to methods by which the bacteriologist is able to detect the presence of the diphtheria bacillus. In pulmonary tuberculosis, also, the bacteriologist can usually detect the tubercle bacillus in the sputa before the clinical expert can recognize with certainty the physical signs of the disease. Scientific physicians in all parts of the world now resort to the use of the microscope and the staining methods by which this bacillus is recognized for making an early diagnosis in cases of this nature. Other diseases in which the recognition of the specific germ establishes the diagnosis are relapsing fever, typhoid fever, glanders, and anthrax—the two last
