SERUM THERAPY, the practice of treating diseases by injecting into the blood, fluid obtained from animals pre viously rendered immune against these diseases. This system of treatment is based upon the theory that bacteria pro duce disease by the formation in the blood, of poisonous bodies known as tox ins. The blood of a healthy animal has the power of combating the effect of these toxins by the production of other bodies known as antitoxins. These antitoxins not only check the course of the disease, but to a large extent render the person who has suffered from any particular disease immune against subsequent at tacks. The object of serum therapy is to produce an artificial resistance to disease by introducing into the blood antitoxins from an outside source.
The most successful application of the theory has been in the treatment of diph theria, and a description of the method of preparing the serum used in this dis ease may be taken as an example. A cul ture of the bacillus which causes diph theria is made in broth, and the toxin is thereby produced. The bacilli are then killed by a weak antiseptic solution and removed by filtration. The filtrate con tains the toxins in solution, and small doses are injected into the blood of a healthy horse. More and more doses are injected at intervals, in ever-increasing quantities. The blood of the horse com bats the poison by producing antitoxins, and the serum is tested, from time to time, by injecting into guinea-pigs, previously inoculated with diphtheria bacilli. When
the serum has reached the required strength, the horse is bled, the serum is separated from the blood, treated with a preservative and measured into stand ard doses. By introducing this serum into the blood of persons suffering from diphtheria the resistance to the disease is greatly increased.
Several attempts to cure other diseases by the use of serums have met with failure. For instance, serums for the treatment of pneumonia, scarlet fever, rheumatism, dysentery, cholera, and an thrax have met with little or no success. On the other hand, tetanus, meningitis, plague and snake poisons have all been successfully treated by this method. An antitoxin for the cure of hay fever has been used with partial success. It is pre pared from animals which have become immune against the effect of pollen from plants or grasses. It is found, however, that there are so many varieties of pollen that no animal can be immune against all of them. In consequence, the serums are frequently found useless owing to the fact that the sufferer from the disease may come into contact with pollen dif ferent from that encountered by the ani mal from which the serum was prepared.
Another use of serum is in the control of persistent bleeding, the normal serum of the horse being found valuable for this purpose. Convalescent serums, prepared from the blood of convalescents from va rious fevers, are also used.