338 MEDICAL BACTERIOLOGY 



In a typical reaction the motility is almost immediately affected, 

 and soon motion ceases altogether while the bacilli collect in clumps, 



FIG. 40. Widal Reaction. I. B, typhosus before adding typhoid blood; II, A typical 

 reaction. 



i. e., become "agglutinated." (Fig. 40.) The usual time limit is 

 thirty minutes when the dilution is 1 to 50. 



REFERENCES, v. J. 45 ; Si. 100. See also texts under particular 

 organism. 



EXERCISE 103. EXAMINATION OF FECES. 



The material expelled from the rectum and comprising the sub- 

 stances from the food and the secretions of the alimentary tract come 

 under this head. The number of micro-organisms occurring here is 

 enormous, and comprise a large number of species and among them 

 several pathogenic forms particularly B. typhosus, Msp. comma, 

 Bact. tuberculosis and Amoeba coli. 



Bacillus typhosus. This organism occurs in the f eces in the case 

 of typhoid patients; but on account of the large number of other 

 organisms its detection is very difficult. The following methods are 

 the most serviceable : 



A. PARIETTI'S METHOD. This method consists in adding Parietti's 

 solution (carbolic acid 5 grams, hydrochloric acid 4 grams, and dis- 

 tilled water 100 cc. ) to bouillon in the following manner : A num- 

 ber of tubes of bouillon have a varying quantity of the above solu- 

 tion added, e. g. 1 drop to one tube, 2 to another, 3 to another, and 

 so on. These tubes are inoculated with a small quantity (one or two 

 loops), of the feces and then placed in the 38 C. incubator. Twen- 



