430 A MANUAL OF BACTERIOLOGY 



already been alluded to (p. 244 ). It is quite likely that in typhoid 

 fever and some other diseases the relapse may be due to the 

 infecting organism becoming " fast " or resistant to the anti- 

 bacterial substances, so that it again grows and multiplies and 

 produces a recrudescence of the disease. 



In the case of relapsing fever the organism is probably a proto- 

 zoon, and in protozoal diseases relapses coincide with develop- 

 mental cycles of the parasite, e.g. in malaria. 



Clinical Diagnosis 



(I) Blood cultures. Five to 10 c.c. of blood are withdrawn 

 from a superficial vein with a syringe with aseptic precautions, 

 and sown into one or two tubes containing 15 to 20 c.c. of broth, 

 or trypsin broth. The tubes are incubated at 37 C., and if 

 organisms develop these are isolated and examined culturally and 

 by agglutination for the typhoid bacillus. Coleman and Buxton 

 recommend the following culture medium : Ox-bile 90 c.c., 

 glycerin 10 c.c., and peptone 2 grm. Distribute in small flasks, 

 20 c.c. in each, and sterilise. Each flask is inoculated with 2 to 

 3 c.c. of blood, incubated for eighteen to twenty-four hours, then 

 streaks from each are made on to litmus lactose agar plates, which 

 are incubated for a few hours. If the growth does not redden the 

 medium and a typhoid-like bacillus is present, it is tested for 

 agglutination with typhoid-immune serum. 



(II) Agglutination reaction. This may be carried out by the 

 microscopic or the macroscopic (sedimentation) method described 

 at p. 232. Dilutions of 1 : 30, 1 : 50, and 1 : 100 should be made. 

 The microscopic method is the more rapid. Various apparatus 

 (agglutinometers) can be obtained, consisting of measuring- 

 devices and a supply of dead culture, with which the sedimenta- 

 tion test can be carried out by any one, but are unsatisfactory 

 in the tropics. 



Garrow's agglutinometer is a very handy apparatus for carrying 

 out agglutinations in typhoid fever and allied conditions (see 

 p. 233). 



Agglutination is now commonly carried out by Dreyer's " Stan- 

 dard Method " (p. 230), the blood serum being tested for typhoid 

 and paratyphoid A and B agglutinations at the same time. The 

 apparatus (supplied by Messrs. Baird and Tatlock, 14, Cross Street, 

 Hatton Garden, E.G.) consists of a small metal stand to hold 16 



