196 ELEMENTARY BIOLOGY 



The use of the antitoxin is coming to be quite general in 

 the treatment of diphtheria, and in the prevention of diphtheria 

 in the case of people who have been exposed to infection. The 

 efficacy of the treatment depends upon its being introduced 

 early enough to neutralize the poison given off by the bacteria 

 before these have gained any headway in the body of the 

 patient. 1 



Antitoxin serums have been prepared for tetanus (lockjaw), 

 for snake bite, for scorpion sting, and for castor-bean poisoning. 



225. Agglutinins. In the case of typhoid fever it was found that 

 if a few drops of the serum from a patient are mixed with a few drops 

 of liquid containing typhoid bacteria, the bacteria are all clumped 

 together in masses, instead of floating about separately. This illus- 

 trates the formation in the blood of a substance that acts upon bacteria 

 by agglutinating them, or sticking them together. Such substances 

 are called agglutinins, and, like precipitins and antitoxins, they are 

 specific. Although the agglutinins do not kill the bacteria, they 

 probably interfere in some way with their action (see Fig. 74). 2 



226. Cytolysins. When the blood of a human being or 

 other backboned animal is examined under the microscope, 

 the red corpuscles and the various white corpuscles are seen to 

 float or move about apparently unaffected by one .another. 

 But if some blood of a different species of animal is injected 

 into the veins of a rabbit or mouse, the foreign red corpuscles 



1 The gain that has come through the discovery of the principle of anti- 

 toxin formation, and through its application, can be measured in terms of 

 reduced loss of life. This may be measured in two ways : 



1. Out of all the population, what is the reduction in the proportion of those 

 that died of diphtheria ? 



2. Out of all the people who get the disease, what is the reduction in the 

 proportion of those that die? 



Both of these sets of facts are given in the diagrams on pages 194 and 195. 



That it is always safest to use antitoxin as early in the history of a case as 

 possible is shown by facts like those given in the diagram (Fig. 73) based on 

 hospital records. 



2 After a mass of typhoid bacteria has been agglutinated by a serum it is 

 still possible to get the same bacteria to multiply in a suitable medium. 



