338 MEDICAL BACTERIOLOGY 



In a typical reaction the motility is almost immediately affected, 

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



Pig. 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. 



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

 organism. 



EXERCISE 103. EXAMINATION OF FECES. 



The material expelled fiom 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. typJiosus, 3Isp. comma, 

 Bad. tuberculosis and Amoeba coli. 



Bacillus typhosus. This organism occurs in the feces in the case 

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

 organisms its detection is very difficult. The following methods are 

 the most serviceable : 



A. Paeietti'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- 



