624 SCIENCE PROGRESS. 



with its much shorter incubation period and rapid develop- 

 ment, we should expect to, and actually do, find the reaction 

 earlier. 



If the normal agglutinin in the blood is of a non-specific 

 character, then an attack of enterica produces an entirely new 

 substance and does not add to what is already present, because 

 the effect of the serum on cholera vibrios and coli bacilli 

 remains the same, only that on typhoid bacilli is increased. 



The rate of agglutinin production varies in different cases 

 as might be expected, and there is also a remarkable varia- 

 tion from clay to day in the agglutinative power of the 

 serum. These variations can hardly be entirely due to 

 experimental errors. In immunising- animals I have often 

 noticed that the agglutinative power seemed to increase 

 irregularly. Moreover, It is known that the agglutinin is 

 used up during its action on the bacilli, this being one 

 reason for always employing a constant quantity of culture. 

 Consequently, it appears possible that a rapid increase in 

 the number of micro-organisms, which may easily occur if 

 they light on some fresh suitable soil, would use up the 

 available agglutinin and reduce the amount temporarily 

 below what it had been the day before and may reduce It 

 below the level of normal blood. And It explains why the 

 most severe cases of typhoid may have comparatively little 

 agglutinin In their blood. 



By the aid, therefore, of a known culture of typhoid 

 bacilli and by suitable dilution of the serum .to be tested 

 to avoid any error due to the presence of normal agglutinin, 

 It is possible to diagnose enterica by the agglutinin con- 

 tained in the patient's blood. It is obvious that the 

 principles of serum -diagnosis apply to other diseases as 

 well as enterica. The method has Indeed been used for 

 the diagnosis of cholera, Malta fever and glanders. In 

 diphtheria and tubercle it has not yet been successful. It 

 might very well be applied also to the diagnosis of pneu- 

 monia, erysipelas, appendicitis and influenza if required, 

 since It Is not necessary that the specific organism should 

 be motile. From a case of scarlet fever I isolated a coccus 

 which agglutinates with scarlet fever serum {7^). 



