IMMUNE AGGLUTININS. 207 



even when the serum is diluted to one in thirty, a 

 point of practical importance in the clinical use of 

 the test. When a normal serum is found to have a 

 high agglutinating power, a previous infection by 

 the micro-organism is to be thought of. This pos- 

 sibility receives emphasis from the fact that the 

 serum of a new-born child is devoid of many of the 

 agglutinins which are found in later life. Hence, 

 of the so-called normal agglutinins, many, after 

 all, may be acquired properties. 



The term immune agglutinin is applied to the immune 

 agglutinating substance in a serum, when the A8rslutinl 

 property has developed as a result of infection, or 

 of systematic immunization with the organism. 

 Thay are formed during infections with the organ- 

 isms of typhoid, cholera, dysentery, plague, etc. 



For the artificial production of agglutinins, the 

 bacteria may be injected into the veins, subcutane- 

 ous tissue, or peritoneal cavity; in some cases they 

 may be fed to animals, rubbed into the skin, or 

 sprayed into the lungs. If certain micro-organ- 

 isms are sealed up in a collodion sac and placed in 

 the abdominal cavity of an animal, an agglutinat- 

 ing serum will be formed ; the necessary substances 

 diffuse through the sac and reach those body cells 

 which produce the agglutinin. It is not necessary 

 that living bacteria be injected ; in fact, the strong- 

 est agglutinin is said to be formed by the injection 

 of bacteria which have been killed by a tempera- 

 ture of 62 C. In certain instances agglutinins are 

 produced by immunization with disintegration 

 products of bacteria or with bacterial extracts. 



Nearly all bacteria, even when non-pathogenic, 

 will give rise to agglutinating serums when in- 

 jected ; but not all have the power equally. Nicolle 



