344 SCIENCE PROGRESS 



pulmonary artery into the lungs again. Most bacilli will lodge 

 where capillary vessels are smallest and the blood stream slow; 

 consequently tubercles are found in greatest numbers at the 

 apex of each lung, where the movements of respiration expand 

 the lung least and where, therefore, blood is pressed out by the 

 lung with least force when this expands and the capillaries are 

 dilated less than elsewhere by lung relaxation during respiration. 



But lung capillaries are wide and many tubercle bacilli 

 escape to return in the bright red oxygenated blood by the wide 

 pulmonary veins to the left auricle. From the left auricle, the 

 bacilli pass into the left ventricle and thence are swept in the 

 full current of arterial blood through wide channels without a 

 bend or branch by the internal carotid arteries to the brain. On 

 the base of the brain, the carotid artery bends suddenly to end 

 abruptly in branches, one of which, the largest — the middle 

 cerebral — continues the direct line of the carotid blood stream 

 and passing up the sylvian fissure supplies the surface of the brain. 



It is precisely along this vessel that most tubercles are dis- 

 tributed in the variety of Meningitis which is under considera- 

 tion. Hard by the spot where the internal carotid springs from 

 the aorta the vertebral artery arises which supplies the upper 

 cervical portion of the spinal cord. Correspondingly, the 

 maximum incidence of tuberculous cerebro-spinal meningitis 

 falls on the anterior aspect of the cervical spinal cord. 



Next in order of infection comes the spleen, itself the blood 

 filter, subserving a function in respect of the blood exactly 

 similar to that of the lymphatic glands on the lymph paths. 

 Elsewhere tubercles are found in all organs in which the blood 

 channels terminate in minute end-arteries — vessels having no 

 free communication with their fellows. Consequently miliary 

 tubercles are found under the capsule of the liver and kidneys. 



In miliary tuberculosis I have never seen miliary tubercles 

 in the supra-renals nor in the pancreas, presumably because 

 these organs possess wide blood channels in free communi- 

 cation with each other, as is also the case in the limbs and 

 body wall. 



Of particular interest in the case considered are the small 

 ulcers in the intestine unassociated with tuberculous deposit in 

 the intestinal glands. 



Presumably, the baby had swallowed tubercle bacilli in 

 his saliva as well as breathed them into his lungs ; at the 



