364: 
agents are applied to the microscopic particle under observa- 
tion without a deluging stream being produced so as to 
carry the particle right out of the field of the micro- 
scope. Such a stream is produced when a liquid is 
allowed to pass under the thin glass cover as ordinarily used, 
but with the gas chamber the reagent acts quietly, and 
without the least inconvenience to the observer, so that he is 
able to retain one individual particle under observation 
throughout the process. A second advantage in the gaseous 
method over that of solutions is, that the action of the 
diluents, water, or spirit is avoided. A third, and perhaps the 
most striking, is, that exceedingly minute traces of a reagent 
can thus be brought to bear and very gradually increased in 
strength whilst the observer is watching the object submitted 
to the reagent ; at any moment the action may be stopped, 
and with the greatest facility and rapidity a second counter- 
acting or other reagent introduced by the use of the second 
tube of the chamber. 
Among the reagents which may thus be used and of which 
I have made some trial are water, hydrochloric acid gas 
(by current of air drawn through its solution), carbonic acid 
gas, acetic acid, osmic acid, nitrogen tetroxide, hydrogen 
sulphide, chlorine, iodine, bromine, ammonia, alcohol, ether, 
chloroform, carbon bisulphide, carbolic acid, and other gases 
and vapours of volatile liquids. © Without now entering into 
further detail, I will merely express my belief that it will be 
found of great importance to apply all reagents used in che- 
‘mical histology in the gaseous form where possible, though, 
of course, it is necessary also to have recourse to liquid 
bodies. 
2. Opinions and doubts concerning the red blood corpuscle.— 
The literature on such a subject as the red blood-corpuscle is 
so extensive that it would be quite out of the question to 
attempt to give here a summary of it. ‘The excellent though 
somewhat partial article of Rollett in ‘ Stricker’s Handbuch’ 
contains a general statement of what has been done and 
thought in the matter. I was led to make the observations 
described below from repeating with Stricker, in the spring of 
last year, his experiments on the action of alternating carbonic 
acid and atmospheric air on the red blood-corpuscle. I thought 
it would be desirable to ascertain whether if the carbonic acid 
were alternated with any other inactive gas a similar result 
could be obtained, and accordingly examined the action of a 
variety of gases and vapours, a consideration of which neces- 
sarily throws some light on the still unsettled points concern- 
ing the structure of the corpuscle. The problems (belonging 
