INTESTINAL GROUP 87 



f) Wash thoroughly in water. 



k) Drain the water off with blotting-paper. 



/) Cover with anilin-gentian-violet or carbol-fuchsin. 



m) Heat as before over a small flame for i J minutes. 



n) Wash thoroughly in water. 



0) Examine in water. 



p) If satisfactory, mount in balsam. 



4. Special study C. — Agglutination. — Dried-blood 

 method of Johnston: A drop of blood of a typhoid- 

 fever patient is obtained by pricking the lobe of the ear, 

 previously carefully cleaned and washed with alcohol. 

 The blood is taken up by a piece of sterile non-absorbent 

 paper or on a sterile aluminum slide. This is sent to a 

 laboratory, where the blood is dissolved in physiological 

 salt solution in such a manner as to obtain an approxi- 

 mate dilution of 1:25. This solution is then tested with 

 a suspension of typhoid bacilli, a young culture of which 

 is constantly kept on hand for this purpose. 



For laboratory tests the serum of an animal (either 

 a rabbit or a guinea-pig) which has been injected with 

 cultures of B. typhosus, previously heated for i hour at 

 60°. This process kills the organisms, but the toxins 

 remain active. The animal is then bled in the following 

 manner: One of the ears is shaved, and the skin is 

 washed with alcohol. A small vein near the border is 

 opened, and the blood is collected in a sterile glass vessel. 

 If the animal does not bleed freely enough, it must be 

 warmed, preferably by means of a hot-water bag. The 

 blood is placed in the ice-chest, and the serum is col- 

 lected after separation. 



The method of procedure with a serum obtained in 

 the above-described manner is as follows: 



