ON THE LYMPHATIC SYSTEM. 163 



themselves into the lymphatics associated with the ducts and 

 the larger blood-vessels of the lobule. 



These relations are well illustrated in figs. 13 and 14, and it 

 does not require any lengthy description to make them under- 

 stood. In all those glands, and in all those places where the 

 interlobular tissue is reduced to thin fascicle plates with the 

 llattened endotheloid connective-tissue corpuscles between them, 

 as mentioned above, the circumalveolar lymph-spaces of the 

 periphery of the lobule open into the lymph-spaces and clefts 

 contained between these fascicle plates. 'The same is also the 

 case where the ducts and the large blood-vessels entering the 

 lobule are accompanied by delicate trabeculse of connective 

 tissue, for the spaces and clefts between these are the paths by 

 which fluid passes from the circumalveolar lymph-spaces of the 

 central portion of the lobule into the efferent lymphatics. 



c. Observations on the Minute Structure. 



The facts which I wish to describe in this section refer to 

 some points in the structure of the ducts and alveoli in the dif- 

 ferent salivary glands, which have not been sufficiently appre- 

 ciated yet or which differ in some respects from those mentioned 

 by other observers, notably Professor Heidenhain, in his admir- 

 able article in Hermann^s ' Physiologie,^ vol. v. As regards the 

 ducts, it is necessary to consider separately the interlobular 

 from the intralobular ducts. The first are the large ducts lined 

 in most glands with a double layer of columnar epithelial cells. 

 The one next to the lumen of the duct, i.e. the inner layer, is 

 composed of conical or columnar cells, each with an oval 

 nucleus in about the middle. The outer layer is composed of 

 inverted conical cells ; the basis of these cells rests on the 

 membrana propria, while the pointed extremity is pushed in 

 between the superficial cells. Each cell possesses in its outer 

 part a spherical or slightly oval nucleus, which is as a rule more 

 transparent than that of the inner layer of cells. In many 

 instances the cell-substance of the outer and inner cells shows a 

 more or less pronounced indication of a longitudinal fibrillation, 

 similar to the one well known since Henle's and Pfliiger's 

 researches in the intralobular ducts (see below), or the salivary 

 tubes of Pfliiger. There are apparently great differences in this 

 respect between the interlobular ducts of the various salivary 

 glands. The outer layer of cells, i.e. the one next to the mem- 

 brane propria, is not in all salivary glands equally distinct ; 

 where this layer is well represented, its nuclei contrast well with 

 those of the inner layer by their spherical shape, small size, and 

 great transparency. 



The following is a summary of my notes on this point : 



