APPLICATIONS OF BACTERIOLOGY 263 



subordinate phenomenon an independent diagnostic test has 

 been estabUshed by making a simple prick in the skin (Moro), 



Further, it is possible to inject into the thickness of the 

 skin itself a drop of the solution containing only y^^ of a 

 milligram of tuberculin ; there is thus obtained a very definite 

 diagnostic reaction : the intradermo-reaction (Mantoux). 



These procedures are all very convenient, especially in the 

 examination of children ; the methods of pricking and of 

 intradermo-reaction are less severe than the intra-ocular 

 instillation. 



The cutaneous reaction of V. Pirquet gives about 85-90 per 

 cent, of positive results in children presenting signs of tuber- 

 culosis, 20 per cent, in children with no clinical symptoms, and 

 48 per cent, in doubtful cases. The percentage of positive 

 reactions in children not clinically tuberculous varies with the 

 'age. During the first 6 months of life it is practically o ; 

 from 6 to 24 months 2 per cent. ; from 2 to 4 years 13 per 

 cent. ; from 4 to six years 17 per cent. ; from 6 to 10 years 

 35 per cent. ; from 10 to 14 years 55 per cent. ; in adults 

 there are at least 77 per cent, of positive reactions. 



The great value of V. Pirquet's cutaneous reaction is that 

 with a little prick, which is itself quite harmless" and produces 

 no trace of fever, and with a minimal quantity of tuberculin 

 (down to xinnj of a milligram), it is possible to tell if a child is 

 affected with tubercle bacillus. 



The younger the child the more definitely does the 

 reaction signify a true active infection, since tuberculosis is less 

 frequent — and more recent — the younger the infant. In the 

 adult, it indicates for the most part a tuberculous impregnation, 

 great or small, recent or remote. 



The cutaneous tuberculin reaction, performed as it has been 

 on thousands and thousands of human beings, has taught us 

 that man becomes infected with tubercle in childhood from his 

 first to his fourteenth yearj so that tuberculosis, although it 

 may only become serious and fatal at a more advanced age, is 

 really a disease of children and not of adult Ufe. It is then 

 during childhood that protection is necessary and since we 



