SEROUS CANALS. 315 



must not be at once cast aside as " artificial products," but they 

 rather show, since their forms cannot be referred to the arrange- 

 ment of the fibrils, that the interfibrillar and interlamellar sub- 

 stance does not possess, in all directions, an equal density, but 

 must consist of a soft fluid mass, and a firmer and more resistant 

 material. From microscopical investigation we learn that the 

 corneal corpuscles are situated in the channels which contain 

 the injection; this must consequently correspond with their 

 natural position, and it follows that these spaces are, at least in 

 certain directions, immensely dilatable, and can scarcely there- 

 fore possess a proper investing membrane. If we take all 

 these facts into consideration, we must, I think, come unavoid- 

 ably to the conclusion, first, that, in the denser organs com- 

 posed of connective tissue, as the cornea, tendons, fasciae, and 

 cutis, the lacunae between the fibres or fasciculi are not filled 

 with fluid alone, but in great part contain a more solid cement- 

 ing substance ; and, secondly, that in this more solid substance 

 there are no cavities constituting matrices for cells, although 

 plexiform canals destitute of walls are present, which are 

 partly filled with cells, and partly with a variable quantity of 

 fluid consisting of the juice of the tissues. 



Since the nitrate of silver, when properly applied, only colours 

 the solid tissues, the serous canals appear as colourless bands, re- 

 sembling the lymph and blood vessels, which can be followed to 

 their finest branches with afacility proportionate to their breadth, 

 or as they happen to be filled more strongly with fluid at the time 

 when they were stained with the silver. We must attribute the 

 incomplete appearance of the plexuses in some cases to the ab- 

 sence of fluid, especially where the wider parts only, in which the 

 connective tissue corpuscles lie, make their appearance. The 

 serous canals have, however, very different forms in the various 

 organs. They appear as distinct plexuses of subcylindrical ca- 

 nals in the dense organs composed of connective tissue, to which 

 reference has above been made, the form of the networks being 

 in accordance with the stratification of the organ ; so that in 

 the tendons and fibrous organs the meshes are considerably 

 elongated in the direction of the fibres, whilst in the cornea 

 they are expanded into layers between the lamellae, and are in 

 communication with one another by comparatively few branches, 



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