Many diseases are introduced into a herd or flock by thoughtlessness on the part of the owner. I have known distemper to be introduced into stables and among horses, Texas fever and tuberculosis into herds of cattle, and hog cholera among hogs, because diseased animals, when purchased, were not separated off by themselves, for a short time at least. If this were done, farmers would lessen the chance of an introduction of disease into their healthy herds. Consequently quarantine quarters should be provided; especially is this true if new animals are frequently purchased and brought to the farm where many animals are raised and handled. These quarantine quarters need not be expensive, and they ought to be removed far enough from the farm stock so that there may be no easy means of infection. When newly purchased animals are placed in the quarantine quarters they should be kept there long enough to determine if anything strange or unusual is taking place. [Illustration: POULTICING THE THROAT The picture shows how to apply a poultice to the throat.] CHAPTER I How the Animal Body is Formed The cell is the unit of growth. It is so with all forms of life--plant or animal, insect or bacterium. In the beginning the start is with a single cell, an egg, if you please. After fertilization has taken place, this single cell enlarges or grows. Many changes now occur, all rather rapidly, until the cell walls become too small, when it breaks apart and forms two cells just like the first used to be. This is known as cell division. As growth increases, the number of cells increases also--until in the end there are millions. =Nature of the Cell.=--The cell is very small. In most cases it cannot be seen with the naked eye. The microscope is necessary for a study of the parts, the nature and the character of the cell. In the first place the cell is a kind of inclosed sac, in which are found the elements of growth and life. Surrounding the cell is a thin wall known as the cell membrane. In plants this cell wall is composed of cellulose, a woody substance, which is thin and tender in green and growing plants, but hard and woody when the plant is mature. Within the limits of the cell is the protoplasm, the chief constituent of the cell; locked up in this protoplasm is life, the vital processes that have to do with growth, development, individual existence. Embedded within the protoplasm is another part known as the nucleus and recognized under the microscope by its density. Around the nucleus is centered the development of new cells or reproduction--for the changes that convert the mother-cell into offspring-cells are first noted in this place. [Illustration: HOW A CELL DIVIDES The simple steps in cell division are pictured here. Starting with a single cell, growth and enlargement take place, ending finally in cell division or the production of two individual cells.]