Mkttam — Studies in Tiiherculom, 



73 



mucous membrane. They must bo conveyed through by some 

 element capable of passing through the epithelium into the lymphatic 

 or blood-vessels. Now, it is a fact that lymphocytes or other forms of 

 leucocytes are frequently passing to and fro through the epithelium 

 into the lacteals placed in the villi of the mucous membrane of the 

 small intestine, or into the lymphoid tissue which forms so large a 

 portion of the structure of the mucous membrane of both small and 

 large intestines. That tubercle bacilli do pass into the lacteals soon 

 after an infective repast is known. Nicolas and Decos found the 

 fluid in the lacteals contained sufficient tubercle bacilli, three hours 

 after an infective repast, to infect a guinea-pig. 



Eavenal found the chyle of a dog that had fed on tuberculous 

 material infective four hours after the meal. The tubercle bacilli in 

 both these cases probably gained access to the lacteals through the 

 agency of cells that had phagocyted them. If this is the case, then, 

 doubtless, lesions should be found in the lacteals themselves; 

 tubercles should develop in these lymphatic vessels as elsewhere. I 

 have been fortunate in finding such tubercles. The animal was a 

 rabbit that I fed upon material from a tuberculous mammary gland of 

 a cow. I killed the animal thirty-eight days later. There were 

 extensive lesions of the intestine and especially close to the ileo- 

 coecal valve, where the mucous membrane was necrotic and ulcerating. 

 Sections of the wall of the gut showed considerable destruction of 

 mucous membrane ; but on the edge of the lesion, where the villi were 

 still intact with the epithelium in situ, I found tubercles present in 

 the lacteals of the villi. The endothelial lining of the lacteal could 

 be discovered without difficulty. The tubercle itself is composed of 

 epithelioid cells, with some few lymphocytes placed especially at the 

 margin of the tubercle. In one section a giant cell was present. All 

 the characteristic elements of the tubercle are present, epithelioid 

 cells, giant cells, and lymphocytes. The tubercle is precisely of the 

 sam^ character as that developing in, for instance, the pulmonary 

 capillaries or along the course of the lymph in the peri-bronchial or 

 peri-vascular lymphatics of the lungs. 



