40 THE STRITCTUBE OF THE LYMPHATIC GLANDS. 



of a granular matter. When these thickened, and dilated vessels 

 are cut, torn, or broken, so as to display their structure, it may 

 be observed that two parts enter into their composition ; an ex- 

 tremely fine external membrane, and a thick granular substance, 

 which lines the membrane. 



The external membrane is extremely thin and transparent. 

 In its substance there are arranged, at regular distances, ovoidal 

 bodies, so placed that their long diameters are all in the same 

 direction. The distance of these bodies from one another is 

 somewhat greater than their long diameters. They are embed- 

 ded in the substance, and form a part of the membrane. They 

 are hollow, and contain one or more rounded vesicles grouped 

 together in their interior. I have seen portions of this membrane 

 after it has been acted upon by acetic acid, present an appear- 

 ance of being broken up into flat semi-transparent scales, united 

 by their edges, each scale consisting of one of the nucleated 

 ovoidal bodies, and a portion of the surrounding membrane. 



The thick granular substance which is attached to the internal 

 surface of the membrane just described, is composed entirely of 

 nucleated particles, closely packed together, and cohering to one 

 another. The thickness of this layer of granular substance is so 

 considerable as to render the vessel, of which it is a part, almost 

 opaque, encroaching on its cavity, and leaving a comparatively 

 narrow canal for the passage of the lymph and chyle. This canal 

 appears to be somewhat irregular, in consequence of the greater 

 exuberance of the granular substance in some spots, and its de- 

 ficiency in others. This circumstance also accounts for the greater 

 transparency of the vessels at certain parts of their extent. The 

 canal is not lined by a membrane, but appears to me to be irregu- 

 larly pierced through the granular substance, the projections and 

 hollows of which, as well as the superficial layer of its nucleated 

 particles, being freely bathed by the lymph and chyle. 



The nucleated particles are on an average about the 5000 of an 

 inch in diameter. They are spherical, and contain a nucleus, 

 which consists of one or more particles. Their walls are very dis- 

 tinct, 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 



