HIS, ON THE CORNEA. 49 
acid solution is treated with zitrate of Barytes. An amorphous precipitate 
of Sulphate of Baryta, insoluble in strong acid and alkalies, takes place, if 
sulphurie acid be present. The presence of chlorides is detected by the 
addition of a little xi¢rate of silver to a drop of the solution of the deposit in 
weak nitric acid. The white precipitate of chloride of silver is insoluble in 
nitric acid, but it is dissolved by ammonia. 
“These will serve as examples of the method of detecting the presence of 
different substances in a very minute quantity of matter. The indications 
obtained in this manner are quite as valuable, and may be relied on with as 
much certainty, as if we were provided with avery large quantity of material 
to work upon; in a single drop of a composite solution, the presence of 
several different acids and bases may be detected.” 
The work concludes with a series of tables for practising 
the use of the microscope and manipulation, with a sort of 
catalogue raisonné of apparatus required in microscopical 
investigation. Dr. Beale’s book will be found an admirable 
assistant to all who have made some little progress in micro- 
scopic investigations. 
Beitrége zur normalen und pathologischen Histologie der 
Cornea. Von Dr. WitHELM His. 1856. 
Contributions to the normal and morbid Histology of the Cornea. 
By Dr. W. His. 
Ir the results arrived at by Dr. His in this unassuming 
little work are confirmed by future observers (and the whole 
style and manner of working of the author lead us to 
entertain a strong expectation that they will be), it will 
prove to be one of the most valuable ‘ Contributions’ which 
has been made for a long time, not only to normal and mor- 
bid histology, but to physiology. For one of the most im- 
portant problems presented to the physiologist at the present 
moment is, what is the influence of conditions upon nutri- 
tion? or, in other words, how far and in what manner can 
the vital activities of the elementary histological components 
of tissues be checked, excited, or otherwise modified by 
influences from without? It is from their bearing on this 
great question that Dr. His’s inquiries appear to us to de- 
rive their preponderant interest, though there are many 
