442 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



of the vessels at certain parts of their extent. The canal is 

 not lined by a membrane, but appears to me to be irregularly 

 pierced through the granular substance, the projections and 

 hollows of which, as well as the superficial layer of its nucle- 

 ated particles, being freely bathed by the lymph and chyle. 



The nucleated particles are on an average about the' 5000th 

 of an inch in diameter. They are spherical, and contam a 

 nucleus, which consists of one or more particles. Their walls 

 are very distinct, especially after being treated with acetic acid, 

 which reduces their size somewhat, without dissolving or 

 breaking them up. 



The layer of particles which has now been described is 

 thickest in the lymphatics towards the centre of the gland. 

 If it be examined in either direction towards the afferent or 

 efferent branches, it will be found to become thinner, and, at 

 last, to be continuous with the layer of flat epithelium-scales 

 of the extra-glandular lymphatics. 



The anatomical relations of the membrane, and its layer 

 of nucleated particles, are identical with those which charac- 

 terise the primary cells or membrane, and the secondary or 

 secreting cells of certain glands. The oval vesicles in the 

 substance of the membrane are germinal spots or centres of 

 nutrition, and the membrane is a germinal membrane. I am 

 inclined to believe the spots on the membrane to be the 

 sources from which the germs of the nucleated particles of 

 the thick layer are derived. These spots are doubtless in a 

 state of constant activity in all lymphatic glands, but must 

 be called into much more vigorous action periodically in the 

 mesenteric glands, during the passage of the chyle. If this 

 be the case, these spots must exert a force by which matter 

 is abstracted from the blood which circulates in the neighbour- 

 ing capillaries, for the purpose of developing a steady succes- 

 sion of nucleated particles. 



The arrangement in the substance of the lymphatic glands 



