FIGURE 117.-Imhoff tanks and sludge drying beds, Emscher District, Germany 118.—Chemical precipitation plant at Worcester, Mass., inlet 119.-Chemical precipitation plant at Worcester, Mass., outlet 120.-Triple contact beds at Hampton, England 121.-Inclined screen, operated by water wheel, Birmingham, PAGE 854 855 855 856 England.. 857 122.-Trickling filters and final settling basin and roughing filter at Hyde, England. 858 123.-Trickling filter at Birmingham, England 859 124.-Removing sludge from a septic tank at Manchester, England 861 125.-Septic tank and chemical precipitation tanks at Rochdale, England 862 126.-Burying sludge from hydrolytic tank at Hampton, Eng land 863 127.-Chemical precipitation tanks at Glasgow, Scotland. Lower end 865 128.-Chemical precipitation tanks at Glasgow, Scotland. Upper 865 end 129.-Intermittent sand filtration bed at Brockton, Mass. 866 130.-Filter bed with sand ridged for winter operation at 131.-Discharge of sewage upon a filter bed at Brockton, Mass. 132.-Red oxid of lead and litharge, being mixed in the manufacture of storage batteries 133.-An effective dust-removing system in the boot and shoe industry. 917 134.-System of hoods and ventilators to carry off the fumes from the furnaces in a foundry. 921 135.-A worker with lead oxid, showing respirator to protect himself against the poisonous dust 925 136. The stone industry 929 137.-Workman exposed to zinc fumes in brass casting, causing FIGURE 145.-Section through autoclave 146.-Bramwell-Deane steam sterilizer 147.-Cross section through steam disinfecting chamber 148.-Longitudinal section through steam disinfecting chamber PAGE 984 984 985 986 988 989 990 991 996 151.-Plan showing the method of installing the double-ended permanganate method. 154. The pot method of burning sulphur 155.-Large stack burner for sulphur, with 15 of the 18 pans 999 PREVENTIVE MEDICINE SECTION I PREVENTION OF THE COMMUNICABLE DISEASES CHAPTER I DISEASES HAVING SPECIFIC OR SPECIAL PROPHYLACTIC MEASURES SMALLPOX AND VACCINATION The prevention of smallpox depends primarily upon vaccination, secondarily upon isolation and disinfection. Vaccination was the first specific prophylactic measure given to man; it produces an active immunity to smallpox (variola). On account of its importance and great practical value this subject will be considered in some detail, for much of the antivaccination sentiment is due to ignorance or misconstruction of the facts. Historical Note.-The credit of giving vaccination to the world is due to Jenner, who proved through carefully planned experiments that cowpox protects against smallpox. This fact had been familiar to the farmers and folk, of England as a vague tradition for a long time. A young girl who sought medical advice of Jenner, when a student at Sudbury, said, "I cannot take smallpox because I have had cowpox"; this remark made a strong impression upon the young medical student. Benjamin Jesty, a Dorchestershire farmer, in 1774 successfully vaccinated his wife and two sons. Plett, in Holstein, in 1791 also successfully vaccinated three children. It was Jenner, however, who through logical and scientific methods proved that a person who has had the mild disease, cowpox, enjoys protection against the serious and often fatal disease, smallpox. Waterhouse and others soon repeated and corroborated Jenner's experiments and helped to establish the soundnessof his conclusions. Jenner made his crucial experiments in 1796, when he transferred the vaccine matter from the hand of a dairy maid (Sarah Nelms) to the arm of a boy about 8 years old-name not given. Sarah Nelms scratched her hand with a thorn and "was infected with the cowpox from her master's cows, in May, 1796.” Jenner transferred the vaccine virus from the eruption upon the hand of Sarah Nelms to the arm of the 8-year-old boy on May 14, 1796. A typical take followed. "In order to ascertain whether the boy, after feeling so slight an affection of the system from the cowpox virus, was secure from the contagion of the smallpox, he was inoculated the first of July following with variolous matter, immediately taken from a pustule. Several slight punctures and incisions were made on both arms, and the matter was carefully inserted, but no disease followed. The same appearances were observable on the arm as we commonly see when a patient has had variolous matter applied, after having either the cowpox or the smallpox. Several months afterward he was again inoculated with variolous matter, but no sensible effect was produced on the constitution." In addition to such direct experimental proof, Jenner inoculated smallpox matter into ten persons who had at some previous time contracted cowpox. In justification of such human experimentation it should be remembered that at that time the inoculation of smallpox matter into healthy individuals was an acknowledged method of preventing that disease. Jenner himself was inoculated when a boy. The question of "inoculation" (with smallpox) as contrasted with "vaccination" (with cowpox) will be discussed presently. With such proof as this Jenner put a popular belief upon a scientific basis. He demonstrated that cowpox is a local and trivial disease in man, that it may be readily transferred from man to man, and that it protects against smallpox. The chain of evidence was complete, but he first proved his thesis to his own satisfaction before he gave it to the world. He said himself: "I placed it on a rock where I knew it would be immovable before I invited the public to take a look at it." Jenner presented the results of his observations to the Royal Society, of which he was a Fellow, but the paper was refused. He then published it in 1798 as a book, modestly entitled, "An Inquiry Into the Causes and Effects of the Variola Vaccinæ, a Disease Discovered in Some of the Western Counties of England, Particularly Gloucestershire, and Known by the Name of the Cowpox." Every student of preventive medicine should read this brief "inquiry" in the original. It may be taken as a model of accurate observation and logical presentation, showing great self-restraint and moderation of an observant, imaginative, and judicial mind. Dr. Benjamin Waterhouse, the first professor of Theory and Practice of Physic in the Harvard Medical School, early became convinced of the value of Jenner's demonstration and obtained some vaccine virus from abroad. On July 8, 1800, he vaccinated his son, Daniel Oliver Waterhouse, then five years old. This was the first person vaccinated in America, so far as existing records show. Thomas Jefferson helped materially to spread the new doctrine in this country, and, in 1806, in writing to Jenner, said: "Future nations will know by history only that the loathsome smallpox has existed and by you has been extirpated." This prophecy has not yet been fulfilled-though eminently possible. VACCINATION Vaccination may be defined as the transference of the virus from the skin eruption of an animal having vaccinia or cowpox into the skin of another animal. For over one hundred years vaccination (from vacca-a cow) was a specific term limited to the introduction of the virus of cowpox into the skin, in order to induce vaccinia and prevent variola. In recent years, however, the term has been used in a generic sense to include the introduction of many different substances in many different ways and for many different purposes. Thus we speak of attenuated or killed bacterial cultures as bacterial vaccines; and the subcutaneous inoculation of organic substances of diverse origin and nature is often spoken of as vaccination. We hear of typhoid vaccines, anthrax vaccines, staphylococcus vaccines, and we read in the literature of animals "vaccinated" with extracts of cancer and other organic substances. For distinction between a vaccine and a virus, see page 344. VACCINE VIRUS Vaccine virus is the specific principle in the matter obtained from the skin eruption of animals having a disease known as "vaccinia" or "cowpox." Vaccine virus is obtained from calves, man, the buffalo, sometimes the camel, and other animals. Cowpox, or vaccinia, is an acute specific disease to which many animals are susceptible, namely, man, cattle, camels, rabbits, monkeys, |