354 IMMUNITY AND GURATIVE IN6ClJ'LA¥r(5NS 



adhei-'e to one another as an inactive " clot" or " lump"); 

 As the- "agglutinating" poison is peculiaf (or nearly 

 so) for each kind of microbe, we can tell whether a 

 patient has typhoid by drawing a drop of his-blood into a 

 tube, and adding some fresh living typhoid bacilli to it. 

 If the patient has typhoid he will have begun to form the 

 "typhoid-agglutinating" or "typhoid-paralysing" poison 

 in his blood, and the experiment will result in the " aggluti- 

 nation " (sticking together in a lump) of the typhoid 

 bacilli. And so we prove, in a doubtful case, that the 

 patient has typhoid. 



The third chemical activity of the blood in dealing with 

 poisonous microbes is also one which is conferred upon it 

 by its living cells when excited by the presence of those 

 microbes. It is the production of a " relish "■ (for so it 

 must be called) which attaches itself to the microbes and 

 renders them attractive to the eater-cells (the phagocytes), 

 so that those swarming amoeba-like floating particles at 

 once proceed to engulf the microbes with avidity. In the 

 absence of the relish (the Greek word for it used by Sir 

 Almroth Wright, its discoverer, is " opsonin "), the eater- 

 feells are sluggish — -too sluggish— in their work. They 

 resemble a child who will - not eat- diry toast, or, at best, 

 only slowly, but will devour rapidly many pieces when the 

 'toast is buttered. It is of the utmost importance to us 

 that our white corpuscles, or eater-cells, should not be 

 'slu^tsh but. greedy. 



••'There are some microbes which will prodiice deadly 

 poison if grown in the clear fluid (serum) of the blood of an 

 ■animal' (as, for instance, thecholera-microbe when grown in 

 the serum of the fr6g's blood),, yet when inoculated living 

 mta the blood of that animal never cause the s%Htest 

 illness? Whyi*' Bdcau'se' they are at once eaten by the 

 tigilaht phagocytes of the blood before they can produce 

 any appreciable ahnount of poisorr. That is easily demon- 



