82 
NOTES AND MEMORANDA. 
wide (“ plus 180° ”) angle of aperture, and in support of his view 
refers to an exj^erience in which a friend with an English low-angled 
glass (50° to 70°) showed “Nasmyth’s membrane” in a section of 
human tooth, which the glass of higher aperture proved to be an 
optical illusion only. “ We often hear the remark,” says the Pro- 
fessor, “ that wide-angled glasses are just the thing for the display 
of lined objects, surface markings, diatoms, &c., but that, owing to 
their short focal length and limited working distance, the trouble 
attending the adjustment of collar, and in general the difficulties 
pertaining to their use, they are iinsuited to the purposes of the 
histologist; while, on the contrary, low-angled glasses of greater 
working distance, requiring no skill in management, are the tools 
with which the real work of the microscope has been and will con- 
tinue to be done ; and such are fondly termed good, honest, and 
reliable ‘ working glasses.’ I can never listen to this line of argu- 
ment without entertaining the suspicion that sloth and inactivity lie 
at the bottom. We never hear astronomers complain of the care they 
are compelled to use in instrumentation ; on the contrary, they pride 
themselves on the accomplishment of being able to work instruments 
requiring a great amount of skill and precision in manipulation. 
The objectives of short working distance originated years ago, when 
German pathologists were in the habit of using common window- 
glass to cover their mounts, and at that time the extremely thin glass 
now so easily procurable was unknown. 
“ A vast amount of work has been done with these ‘ honest and 
reliable working glasses,’ and will have to be done over again ; and 
this revising work is now in progress.” 
The Professor also refers to a case in which a sample of urine, 
from a child supposed to be suffering from a disease of the kidneys, 
appeared, when examined with a low power (^, of 70° aperture), to be 
in every respect healthy, “ but on further examination with a wide- 
angled glass, and with an amplification of nearly 4000 diameters, it 
was found to be literally swarming with vibriones.” 
Neic Process of Colouring Microscopic Preparations with a Picro- 
aniline Solution.^ — Whilst engaged on the normal structure of the 
general lymphatic system, I had occasion to communicate to my col- 
leagues of the Societe medico-physique of Florence the good results 
which I had obtained in my investigations (better than by any other 
colouring matter) by a solution of aniline blue and of picric acid. I 
was unable at that time to enter much into details concerning this new 
and most simple method of staining, having only experimented upon a 
single tissue, that of the lymphatic system. Now, however, after 
having, together with Dr. Brigidi, made a large number of observations 
upon almost all the different tissues, I can speak about the method 
with more detail, and recommend it to those who are occupied with 
histological studies. 
The two substances which I recommend for producing a very 
beautiful green colour have been already emploj^ed for some time in 
* Dr. A. Tafaui, in the ‘ Jourmil de Micrograpliie.’ 
