266 TUBERCULOSIS. 



tending beyond the edges of the introduced tissue. It is to be 

 recommended that the tubes of serum be kept in the horizontal 

 position during incubation, lest on account of the low density of 

 the medium, the upright position should damage the extent of 

 surface necessary for growth. 



(4) Agglutination. —^Within the last three years Arloing and 

 Courmont announced that they had been able to obtain aggluti- 

 nation of the tubercle bacillus with the blood serum of tuber- 

 culous patients, in a manner analogous to that introduced by 

 Gruber and Widal in the diagnosis of typhoid fever. The tech- 

 nique is full of difificulties and the reaction is not often obtained 

 in dilutions of i in 25, but usually much lower, as i in 10, i in 15. 

 C. Fraenkel, Neisser, Dieudonnd, Beck, and Rabinowitsch have 

 shown that the reaction is unreliable, being often absent in 

 patients undoubtedly tuberculous. And quite recently Koch 

 has demonstrated that the reaction may appear in non-tuber- 

 culous cases in dilutions of i in 25, or in one case (muscular 

 rheumatism) as high as i in 50, and he fully agrees with the 

 others above cited that the reaction is too uncertain to be of 

 any practical value. Furthermore, it is of interest that serum 

 which agglutinates tubercle bacilli will agglutinate also many of 

 the other acid-resisting bacilli which for this and other reasons 

 may be regarded as allied to B. tuberculosis. 



