128 VETERINARY BACTERIOLOGY 



of bacteriolysins, substances which will dissolve or destroy bacteria. 

 Opsonins (Gr. opsonein, to prepare for eating) are antibodies 

 which will unite with the bacteria and enable the phagocytes 

 to take them up and destroy them. Acquired immunity may, 

 therefore, be said to be either antitoxic, bacteriolytic (antibacterial)., 

 or opsonic, or a combination of any or all of these types. Three 

 other types of body reactions are also generally considered in a 

 discussion of immunity. Although they probably in no instance 

 actually account for immunity, they are found very useful in 

 diagnosis, and their consideration is quite essential to a full dis- 

 cussion of theories of immunity. The blood-serum of individuals 

 suffering from certain infections, particularly bacterial, acquires 

 the property of agglutinating or clumping these organisms. The 

 blood-serum from a horse having glanders when dropped into a 

 culture of the glanders bacillus will cause the bacteria to clump 

 together and settle out, leaving the medium clear. The phenom- 

 enon of agglutination is used in the diagnosis of this and other 

 diseases. A somewhat similar body reaction is provoked by the 

 injection of soluble proteins derived from some other species of 

 animal (or plant) into the body of an animal. The serum of such 

 an animal acquires the property of precipitating the corresponding 

 protein when mixed with it in a test-tube. This phenomenon 

 of precipitation is made use of in the differentiation of many kinds 

 of proteins. The presence of certain substances in the blood, 

 usually proteins derived from any foreign source, may result in 

 the sensitization of the body to such, rather than immunity. This 

 phenomenon is known as anaphylaxis (Gr. an, against; phylasco, 

 to guard) and has led to an explanation of many otherwise obscure 

 pathological and bacteriological facts. 



