176 CLINICAL BACTERIOLOGY. 



disease present is typhoid fever, pure cultures may thus be 

 obtained at once, which do not coagulate milk and do not 

 generate gas in peptone-bouillon. In rare cases of mixed 

 infection, in addition to typhoid-bacilli the streptococcus 

 pyogenes or the staphylococcus is also found in the fluid 

 from the spleen. The method of puncturing the spleen is 

 the same as that employed in every other form of explora- 

 tory puncture. On aspiration the splenic fluid, mixed with 

 blood, is readily obtained, and this is injected into a sterilized 

 dish, five agar-tubes being each then smeared successively 

 with a drop of the fluid ; with the remainder plates are made, 

 and milk-flasks and peptone-bouillon tubes are inoculated. 

 Notwithstanding the trustworthy character of its results, 

 puncture of the spleen is, however, not to be recom- 

 mended. The procedure is by no means free from danger. 

 It should not be forgotten that the typhoid-bacillus is also 

 capable of pyogenic activity, and that the puncture-track 

 in the spleen may give rise to purulent complications, 

 possibly in the peritoneum. 



The most valuable service in the clinical diagnosis of 

 typhoid fever appears to be rendered, however, by the pro- 

 cedure of Widal, who, as has already been mentioned 

 (p. 66), showed that also the blood-serum of typhoid 

 patients yields the agglutination-phenomenon of Gruber. 

 Blood-serum from the patient suspected to be suffering 

 from typhoid fever is obtained by aseptic puncture of the 

 tip of a finger, or of a vein by means of a sterilized syringe. 

 The blood thus obtained is permitted to flow into a test- 

 tube, and to coagulate in a slanting position ; in this way 

 the largest proportion of serum will be obtained. The test is 

 then made according to one of the methods described on 

 page 64 ; the one preferred is a matter of indifference. 

 The desired information is gained most quickly through 

 the microscope, and only by this means is it possible to 

 determine the extreme limit of agglutinating activity that 

 is, the highest degree of dilution of the serum with which 

 the reaction can still be induced. It has been emphasized 

 that the reaction of Gruber is a quantitative one, and that, 

 therefore, everything depends upon determining quantita- 

 tively with precision the agglutinating activity of the 

 serum. A proportion of I to 50 is sufficient for the posi- 

 tive diagnosis of typhoid fever. Many thousand specimens 

 of serum have now been examined according to the method 



