LEUCOCYTES AS CARRIERS. 105 



occasional individuals, without doubt, reach the cir- 

 culation; this, however, is not necessary for the 

 general intoxication. 



Leucocytes are continuously passing from the Leucocytes 



., r , , . n i a Carriers. 



tonsils, intestines and other superficial organs 

 which are rich in lymphatics, through the mucous 

 membrane to the surface. These excreted leuco- 

 cytes may often be seen engorged with large num- 

 bers of bacteria which they encounter on the sur- 

 face, and it has been suggested that the excreted 

 leucocytes may? re-enter the adjacent tissue, carry- 

 ing bacteria with them. The study of sections of 

 the intestines, tonsils and peribronchial lymph 

 glands has shown that bacteria are continuously 

 entering the body, even in health, and their fre- 

 quent occurrence within leucocytes which are near 

 the surface suggests that the latter are the agents 

 through which they are introduced (Buffer, Biz- 

 zozero and others). This finding, however, could 

 not be accepted as proof of the hypothesis, since 

 the phagocytosis may have taken place after the 

 organisms had penetrated the surface independ- 

 ently. 



Through the work of Nocard, Eavenel, Behring 

 and others, it has been shown that tubercle bacilli 

 will pass into the lymphatics from the intestines, 

 in the absence of mechanical defects. 



That the leucocytes may perform this function 

 is also suggested by A. B. Macallum's study of the 

 absorption of iron. When the albuminate and pep- 

 tonate of iron were fed to starved lizards, the min- 

 eral, eight hours later, was demonstrated in large 

 quantities in the leucocytes contained in the lumen 

 of the intestines, also within leucocytes which lay 

 between the epithelial cells of the villi (re-entering 



