MECHANISM OF INFECTION IN TUBERCULOSIS 341 



the attacks of pathogenic micro-organisms. Witness also the 

 extreme susceptibility of the periosteum of the thigh and shin 

 bones to acute streptococcal infections. Furthermore, the ends 

 of the long bones are richly supplied with blood moving through 

 wide spaces in a comparatively stagnant stream ; bacilli reaching 

 the bone by this route are pre-eminently liable to lodge amongst 

 the intricacies of the bony lattice which is being built into the 

 growing bone. These parts too in children are subject to direct 

 injury and this is true of the lower limbs to a greater extent than 

 the upper, a fact in correspondence with the more frequent 

 incidence of tuberculosis at the hip and knee. 



There is no more remarkable nor uniformly fatal form of 

 tuberculosis in children than acute miliary tuberculosis. In 

 this disease, tubercle bacilli reach the blood stream in large 

 numbers and being carried to all parts of the body give rise to 

 tiny tuberculous foci scattered through every organ, hence the 

 term miliary— like millet seed. When the brain is also affected, 

 as is usually the case, we have the condition known as Acute 

 Hydrocephalus or "Water on the Brain" — called technically 

 Tuberculous Meningitis. 



Much may be learnt from careful consideration of the exact 

 distribution of the tuberculous lesions in these cases and such 

 investigation is of special value, seeing that death within three 

 weeks, seldom longer, is their invariable consequence. 



The determining factor in the invasion of the blood by 

 tubercle bacilli and its dissemination in the vital organs remains 

 a matter for conjecture. In no way is it correlated with the 

 number or extent of pre-existing lesions. 



It has been my experience in making postmortem examina- 

 tions of cases of tuberculous meningitis that but one lymphatic 

 gland or group of glands has shown evidence of tuberculosis. 

 Occasionally this gland is to be found in the mesentery, in which 

 case it may be inferred that tubercle bacilli effected an entrance 

 through the gut : most frequently it occurs in the bifurcation 

 gland described above, which is often the only seat of tuberculous 

 infection. 



The following case may be quoted in some detail in illustration : 



A baby aged eleven months, which had always been fed at 

 its mother's breast, was brought to hospital with the story 

 that it had sustained a fall on its head fourteen days before 

 admission but neither at the time nor during the next few days 



