Mémoire publié à l’occasion du jubilé de E. Metchnikoff. 
CONTRIBUTION TO THE STUDY 
OF DELAYED OR “ LATENT ” TUBERCULOUS INFECTION 
by S. DELÉPINE, 
Director of the Public Health Laboratory, University of Manchester. 
In the course of an investigation which brought the writer 
face to face with certain aspecls of latent infection, he observed 
sonie facts upon which the classical observations of Metchnikoff 
on Tuberculosis in lhe Meriones throws much light. Although 
the following spéculative contribution is unwortby of the great 
master, its subject is not altogether inappropriate to the occa¬ 
sion which has caused it to be written. 
The démonstration of the inoculability of Tuberculosis by 
Villemin, and the discovery of Koch’s Bacillus, are lhe bases 
upon which our présent knowledge of the etiology of Tubercu¬ 
losis has been firmly established. It must, however, be 
acknowledged that these fundamental facts are not sufficient to 
explain fu 11 y the distribution of the disease. Our knowledge of 
the factors which, under ordinary circumstances, détermine the 
incidence of the disease, is slill very incomplète. The fact that 
under experimental conditions it is possible to produce tuber¬ 
culosis in a normal animal by inoculation, inhalation or 
ingestion of pure cultures of tubercle bacitli, may for a short 
time hâve led some inexperienced observers to believe that the 
pénétration of Koch’s Bacillus into human tissues was sufficient 
in itself to produce Tuberculosis. If this were true, there would 
be very few persons free from the disease, for its bacillus is so 
widely distributed that the members of a civilised community 
who hâve not at one time or another inhaled or swallowed 
tubercle bacilli must be very few indeed. 
The ubiquity of the tubercle bacillus has led certain 
statisticians to émit the view that, as regards the occurrence of 
