238 LABORATORY EXERCISES IN BACTERIOLOGY. 



and remove them. Antitoxins are substances which are developed mainly in the 

 blood-serum during the course of an infection, which have antagonistic influences upon 

 the toxins of disease (either passively, as when before the introduction of a toxin into 

 an animal body it may be uniformly rendered innocuous by mixture with serum 

 containing the antitoxin, in which action the latter may be thought of as distinctly 

 antidotal and protective ; or actively, where after the introduction of an infection into 

 the animal its effects are overcome by introduction of a certain amount of the anti- 

 toxic serum, although a mixture of the same proportions of toxin and antitoxin out- 

 side the body and its introduction into a smaller animal are followed by the usual 

 effects of the infection. In this latter form the antitoxin apparently stimulates 

 some elements of the infected body to a direct antagonism or is, in other words, 

 healing in its influence). 



9. Agglutination Phenomenon. In this same connection may be considered 

 the agglutinating phenomenon of serums of persons infected or recently well of various 

 diseases, as typhoid fever, over the bacteria of the same specific disease. This mani- 

 festation depends upon some directly bactericidal .substance (contrasting with the 

 antitoxins which antagonize rather the poisons of the bacteria in the serum) ; in some 

 instances actual bacterial destruction (bacteriolysis} may take place, while in others 

 rather a paralyzant influence is exerted upon the organisms as is seen in the stoppage 

 of movement of the germs. Where such bactericidal substances are powerful and 

 persistent in the serum of the patient, the immunity granted to the individual is like- 

 wise persistent. The nature of these substances is not understood. 



Exercise 67. After the tenth day of the disease in typhoid fever, a 

 finger is well cleansed and dried and pricked so that several large drops of 

 blood may escape. These are caught in a clean glass tube, as in an ordi- 

 nary dropper or in a capillary tube. This blood is allowed to clot and the 

 serum to separate (if a capillary U-tube is used it may be centrifugated for 

 the separation). 



A twenty-four-hour bouillon culture of the typhoid bacillus is made. 

 With a capillary pipette of the same caliber as that used for the collection 

 of the serum a suitable amount of the culture is withdrawn. (Care is to be 

 taken to plug the upper end of the pipette with cotton to prevent accidental 

 suction of the culture into the mouth of the operator.) A certain length 

 of the serum tube is now broken off (after filing) and its contents blown 

 out into a watch-crystal (one centimeter length broken off, and serum ex- 

 pelled by holding the broken part in forceps and blowing it out with another 

 fine tube inserted in end) . Fifty times this amount (ten centimeters length 

 taken five times) of the bouillon culture are added to the serum, mixed, 

 and a drop placed on the slide and covered (hanging drop may well be 

 made). These proportions vary with different observers, as weak a dilu- 

 tion as one to ten having been originally practised. At the close of varying 

 periods, ranging from fifteen minutes to as much as two hours, according 

 to various directions, the typhoid bacilli will be found to have ceased from 

 active movement and to have agglutinated in clumps. Extreme limits of 



