PROGRESS OF MICROSCOPICAL SCIENCE. 
245 
7. That, so far as our investigation lias yet gone, it would appear 
that the germs originally present in the solution are destroyed by 
direct insolation. 
We are still pursuing the inquiry, and have devoted much time to 
investigating the influence of the refrangibility of the ray, hut regret 
that at present we are not in a position to give any definite conclusions 
on this point. 
We are endeavouring also to trace an analogy between facts which 
we have observed and certain vital and chemical processes, in which 
light is known to play a part, and are extending our observations to 
other phenomena of fermentation and to microscopic fungi. 
That light is not essential for the development of Bacteria has 
been long known, but that it is absolutely inimical to their production 
has not, so far as we are able to ascertain, been previously shown. 
The Lymphatics of the Shin. — Dr. Mrs. Hoggan and Mr. Hoggan, 
M.B., have lately sent a paper on the above subject to the Royal 
Society (June 14), of which they have been so good as to forward to 
us the following abstract, in which they 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 described as layers ; the second consists of horizontal 
and vertical sets of vessels, extending through the whole thickness of 
the dermis, and connecting 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 subepidermic 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 lymphatics, the function of the nerves 
found upon them cannot be affirmed by the authors. Neither sweat- 
glands, sebaceous glands, hair-muscles, fat-cells, or nerve-bundles, 
possess any lymphatics, and the papilla: 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 cre- 
nated 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, 
