1877.] 



On the Lymphatics of the Mammalian SHn. 



289 



I. "On the Minute Structure and Relationships of the Lym- 

 phatics of the Mammalian Skin, and on the Ultimate Distri- 

 bution of Nerves to the Epidermis and Subepidermic Lym- 

 phatics." By George Hoggan, M.B., and Frances Elizabeth 

 Hoggan, M.D. Communicated by Dr. William Farr, 

 F.R.S. Received May 11, 1877. 



(Abstract.) 



The authors state that, by means of certain modifications in known 

 methods of histological research, a full description of which they offer, 

 they have been enabled to show the minute structure and relationships of 

 the lymphatics of the skin in mammals. 



For the purpose of anatomical description, they divide these lymphatics 

 into three categories, named, from their position, the subhypodermic, 

 the dermic, and the subepidermic. Only the first and third can be de- 

 scribed as layers ; the second consists of horizontal and vertical sets of 

 vessels, extending through the whole thickness of the dermis, and con- 

 necting the other two distinct layers together. 



All the lymphatics of the hypodermis, and most of those of the dermis, 

 are valved efferent vessels, without any collecting channels that would 

 entitle them to claim any absorbing function in these portions of the 

 skin, through which they merely pass. 



The subepidermic lymphatics are narrow parallel collecting channels, 

 destitute of valves, lying, as their name implies, immediately under the 

 epidermic cells in young animals, although separated from them, as adult 

 life is reached, by bundles of gelatinous tissue. These are the only 

 radicles of the lymphatics of the skin. 



Upon the subepiaermic lymphatics they find a rich plexus, formed by 

 multipolar nerve-cells and non-medullated nerve-fibres, the distribution of 

 which to the epidermis has been made evident by the same process. As 

 no acknowledged contractile elements enter into the walls of these lym- 

 phatics, the function of the nerves found upon them cannot be affirmed 

 by the authors. 



Neither sweat-glands, sebaceous glands, hair-muscles, fat-cells, nor nerve 

 bundles possess any lymphatics, and the papillae in the human skin are 

 equally destitute of them. Functionally, the lymphatics of the skin are 

 to be considered as forming two classes, the valved efferent vessels with 

 independent walls, formed only of crenated endothelium cells, and the 

 valveless collecting channels of the subepidermis, lined by those crenated 

 cells. 



Upon the facts accumulated in this and their former paper the authors 

 are led entirely to reject the theory of vasa serosa or radicles of the 

 lymphatics, formed by chains of connective-tissue cells or the cavities in 

 which they lie. In the human skin especially these cells of the connec- 

 tive tissue are numerous and in intimate relationship with the superficial 



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