In collecting specimens of blood for complementfixation reactions it is important to prevent contamination of the serum with certain foreign materials which might vitiate or change the results. In hospitals and laboratories, where the proper instruments and utensils for bleeding the patient and collecting the blood are usually available, such contaminations rarely occur. It is, however, not always possible or convenient to send the patient to a hospital for this purpose and the specimen must be collected at the physician's office or at the patient's home. This is often attended with difficulties, and a poor or worthless specimen is frequently obtained. In other instances there is delay in getting the specimen to the laboratory, which may be situated at a more or less distant point; and, unless the blood and container are sterile, the growth of microorganisms soon renders the specimen unfit for the reaction.
To meet these practical difficulties,