344 MEDICAL BACTERIOLOGY 



of peptone water (Dunham's solution) and incubated at 38 C. 

 The surface growth 6-12 hours later is to be examined microscopi- 

 cally and by means of plates. Then test the peptone cultures for 

 nitroso-indol (cholera red reaction) by the addition of a few drops 

 of sulphuric acid. 



B. dysenteriae. This organism has been isolated from the feces 

 of dysentery patients by numerous investigators and from children 

 suffering from summer diarrhoea by Duval & Bassett 1 and others. 

 The following method is recommended : 



Agar plates are made from the bloody mucus in the feces or 

 from scrapings of the ulcerated mucosa of the intestines. Agar 

 plates are made and incubated at 38 C. for 12 hours and then the 

 colonies which have appeared are marked with a pencil or pen and 

 then the plate is incubated for several hours longer. The colonies 

 which appear later are most likely to be colonies of B. dysenteriae. 

 The suspected colonies are then put into dextrose agar and only 

 those which fail to produce gas are tested farther. The crucial test 

 is the Widal reaction which can be made with blood obtained from 

 the patient or cadaver. 



Bacterium tuberculosis. This organism has been found in the 

 stools in cases of intestinal ulcerations, and may come, in cases of 

 phthisis, from ingested sputa. 



Ameba coli. 



a. A drop of the mucus portions of stool is placed on a glass 

 slide, covered with a cover-glass and examined with a magnification 

 of about 500 diameters (1-6 in objective). Examination should be 

 conducted on a warm stage in order to get ameboid movements. 



Z>. Preparations may be stained with methylen blue and carmine. 

 The nucleus is stained with carmine. 



c. Discharges may be hardened and stained by Mallory 's method 

 as follows : 



1. Fix tissues in alcohol. 



2. Stain (paraffin) sections in a saturated aqueous solution of 

 thionin for 5-20 minutes. 



3. Wash in water. 



4. Differentiate in a 2% aqueous solution of oxalic ocid %-l 



minute. 



5. Wash in water. 



1 Duval and Bassett, Amer. Med., 1904, 4: 417. 



