New Paraboloid Illuminator, &c. By James Edmunds, M.D. 83 
some loose corpuscles. Upon this specimen I have based the de- 
scription given above. I regret that, owing to the absence of sun- 
light at the critical time, and my own want of a heliostat, I could 
not get light enough to define the character of the nebulous points 
in the serum, or to determine the question as to their motility. 
Certainly, however, this serum contained no moving forms such as 
would ordinarily be recognized as Bacteria. The serum was quite 
free from that mere chylous milkiness often seen in blood drawn 
soon after a full meal. 
Salivary corpuscles show up magnificently as spheroids of all 
sizes floating in a sky intrinsically dark, but lighted up by tracts of 
“ milky way,” and flecked with masses of heavy greyish-white cloud. 
The corpuscles, instead of being distorted by foreshortening into 
mere disks, appear as self-luminous spheroids, like moons, their 
nucleolar matter distinctly visible inside the sphere, and each one 
giving an image free from distortion by its own lenticular action 
on transmitted light. The “ milky way ” is like the opaline haze 
of the blood-serum, but not uniformly diffused through the field, 
and consisting of spheroidal particles rather than points, some of 
the spheruloids approaching in size and character to the corpuscles 
which alone are ordinarily seen. The heavy clouds are “ epithelial 
scales,” appearing, however, not as scales, but rather as irregular 
dodecahedral masses, and each one revealing from within a micro- 
cosm of its own. 
In using a balsamed object with a very fine dry sixteenth by 
Powell and Lealand, no light whatever comes up through the 
cover except that which is seen in the microscope by the radiance 
of the object itself — the background remaining a soft black. With 
their new immersion eighth or sixteenth the appearance in the 
microscope is exactly the same, but the drop of water before the 
lens glows with horizontal radiance so as to become a sparkling 
and conspicuous object at many paces distance. 
The first lens made for me by Messrs. Powell and Lealand was 
cut so perfectly as to answer exactly to the theory of its design. 
But this lens being calculated for a slide one-sixteenth of an inch 
in thickness, of course only gives light up to an angle of about 80° 
— a large belt of surface below the latus rectum having been cut 
away. These gentlemen are now making for me a second lens 
with the apex cut off at a point only one-fiftieth of an inch below its 
latus rectum, and, with such a lens, objects may be illuminated with 
light nearly up to their own horizon. But the mounting must be 
such that the object with its vehicle, slide, and subjacent film of gly- 
cerine, must come within the thickness of one-hundredth of an inch 
so as to allow a second hundredth of an inch in vertical sub-stage 
movements, for the purpose of altering the focus of the paraboloid 
when it requires to be exactly centred to the optic axis. If light 
