150 LETTERS TO BROTHER JOHN. 



branches, into the substance of the lungs. Here it 

 is acted upon by the air in the cells of the lungs, 

 loses its characteristics of chyle, and becomes blood. 

 It now turns round, as it were, and hurries back 

 again out of the lungs, along the pulmonary veins, 

 to the left cavity of the heart. 



But before we trace its progress any further, let 

 us suppose that a hungry absorbent has just carried 

 off a single particle from the point the extreme 

 protuberant tip of your organ of smell " the very 

 topmost, towering height o' Johnny's nose" The 

 carrying off this particle would necessarily leave a 

 little hole. Now let us go back for our little glo- 

 bule of blood, which we have just traced from the 

 lungs to the left cavity of the heart. 



Rejoicing in its new existence, it leaps out of the 

 heart into the aorta, hence into the carotid artery, 

 thence into the external carotid, thence into the 

 facial, thence into the superior coronary, and thence 

 into a minute branch which the superior coronary 

 gives off; which branch takes its course toward the 

 tip of your nose. 



By the time the artery, along which the little 

 globule of blood is travelling, has nearly reached 

 the tip of your nose (worthy to be called proboscis), 

 it has become exceedingly minute, and its course 



