70 ANTIBODIES, IMMUNITY, WASSERMANN SERUM TEST 



line, and are finally completely dissolved. These occurrences are 

 called: 



Immobilization (loss of motility). 



Agglutination (becoming glued together). 



Lysis (solution). 



It can be shown that all of these processes favorable to the infected 

 animal, but detrimental to the pathogenic infecting bacteria, are 

 brought about by definite bodies contained in the blood serum and 

 juices of the system. These substances are known as agglutinins and 

 lysins. If human blood serum is injected repeatedly into the body of 

 a rabbit at intervals of ten to fourteen days, and some time after the 

 injection a little of the rabbit's blood serum is obtained, it will be 

 found that a very small amount of the rabbit's blood serum added 

 to a very dilute solution of human blood will cause a clouding or pre- 

 cipitation of exceedingly fine flocculi. Something has evidently been 

 formed in the rabbit's blood serum which precipitates something from 

 the human serum. The body or bodies so formed in the blood serum 

 of one animal treated with the serum of another animal are called 

 precipitins. 



The specific test with the blood of a rabbit sensitized against human 

 blood serum is a very important one from a medicolegal or forensic 

 standpoint, because it makes possible to identify human blood stains 

 in criminal cases and to differentiate them from the blood of any 

 other animal. This test is much more delicate than measuring the 

 erythrocytes in order to distinguish between human and other red 

 blood corpuscles. 



The three bodies, agglutinins, lysins, and precipitins, like opsonins 

 and antitoxins, belong to the protective substances of the animal 

 body against pathogenic bacteria. A common name for all of these 

 bodies inimical to pathogenic bacteria is antibodies. Many anti- 

 bodies are normally present in higher animals, but often only to a 

 small extent and sometimes not at all. However, the system can be 

 stimulated to manufacture antibodies when not present, or to in- 

 crease enormously those present to a small extent, by the injection 

 of either live or dead pathogenic bacteria. Such injections must 

 be practised with certain precautions and with the observation of 

 certain rules, otherwise instead of strengthening the animal against 

 bacterial invasions, it will be killed. The effect of injecting live or 

 dead bacteria into an animal is very different from injecting certain 

 chemical poisons. An animal can be accustomed to stand succes- 

 sively increasing doses of morphine, strychnine, arsenic, etc., but in 

 spite of such treatment, no antibodies to morphine, strychnine, or 

 arsenic are formed. The antibodies formed when pathogenic bacteria 

 are injected are specific, i. e., when, for instance, tetanus bacilli are 

 injected antibodies are formed against tetanus bacilli and their 

 toxins, but they have no effect on diphtheria, glanders, or anthrax 

 bacilli. If it is desired to form antibodies against a certain bacillus, 



