MICROSCOPY. “04 
power it is found to consist of pavement and ciliated columnar epi- 
thelium and a homogeneous, transparent, albuminous substance, 
(never truly fibrous) entangling detached epithelial cells or their 
contents, fat, mucous corpuscles, and a few foreign bodies. These 
casts rarely contain fungus spores ; continue probably to be thrown 
off soon after their formation ; and appear to partake rather of the 
nature of an excessive cell proliferation than of a true exudation : 
they are essentially an epithelial layer cast off and resembling the 
skin shed by some of the lower animals. 
On the other hand, Dr. Bruce and Mr. Golding Bird stated that 
they had never noticed epithelium in the croup membrane, but that 
they had observed an infiltration of exudation cells (white blood ` 
corpuscles). 
“ UNUSABLE” Ossectives.— Mr. Henry U. Janson writes to the 
‘t Monthly Mic. Journal” proposing the wet front, or “aquatic noz- 
zle? as a cure for “unusable sixteenths” and other objectives 
whose angular aperture has been increased at the expense of work- 
ing focus until they can no longer come within reach of a large 
proportion of mounted objeets. Being accustomed to work upon 
diatoms with a moderate angled y, he was induced to procure an 
improved lens of the same power, but 175° angle. This “ tremen- 
dous 175°” performed beautifully upon all that it could reach, but 
about half his extensive collection of diatoms was out of its reach 
by reason of thickness of cover-glass ; and all his high power ob- 
jects have long been labelled “ ” and ‘*O. +,” to indicate whether 
the new or the old sixteenth should be used upon them. Finally, 
having his new ;/, changed into an immersion he found that not 
only was the brilliancy of its performance increased and its power 
raised to about z1,, but that its focus was so much elongated that 
all his O. ;4, objects became perfectly usable. The comparatively 
long working focus of immersion lenses is a convenience well 
known and appreciated, but it has not, perhaps, been hitherto so 
formally recommended as a cure for the (also well known) ‘unus- 
able” dry lenses of large angle. 
Movuntine ry Batsam.—Mr. C. L. Jackson mounts his balsam 
objects in a chloroformic solution of balsam, and, after the air 
bubbles have all escaped, bakes them for about two days upon the 
flat top of a copper or tin box about a foot square and two and a 
half inches deep, and filled with water which is kept by means of 
