174 NOTES AND MEMORANDA. 
he had on exhibition the navicula angulatum resolved into 
dots all over the field, which was apparently more than six- 
teen inches across. By the aid of an amplifier we also gain 
a greater focal distance, and an increase of flatness of field. 
Amplifiers have been employed in telescopes for the past 
fifty years, but ten or twelve years ago they were only 
adapted to microscopes, in this city at least, by one or two 
amateurs. Subsequently, Mr. Tolles, of Boston, saw them 
in use here, and on his return home made one, apparently 
with gratifying success, as he has since kept them im stock. 
Dr. J. G. Richardson inquired of Dr. Hunt whether, in 
his opinion, the four-tenth objective associated with his 
amplifier, as he had it upon the table, and eye-pieced so as 
to give a power of 800 diameters, was equal to his Powell 
and Leland’s one sixteenth immersion lens, combined with 
the “A” eye-piece. Dr. Hunt replied that on histological 
work the results were not quite so good, but on pleurosigma 
angulatum he considered them fully equal. The combination 
of amplifier and objective which he used was, however, a 
merely accidental one, so that a skilful optician would pro- 
bably be able to arrange the lenses more efficiently, and at a 
lower cost. Pigott’s aplanatic searcher appeared to be a modi- 
fication of the amplifier, but had proved so unsatisfactory in 
his hands that he had entirely laid it aside. 
Professor Stricker on Pathology of Suppuration.— For some 
time past Professor Stricker, of Vienna, has been conducting 
a series of investigations on the pathology of suppuration of 
the cornea. An account of his results has been published 
in the December number of ‘ Stricker’s Medizinische 
Jahrbiicher’ for 1874. Mr. D. J. Hamilton, who has been 
working on the subject of inflammation, during the present 
winter in his Laboratory, sends us the following account of 
the methods of procedure and the appearances met with. The 
cornea of the kitten is the most convenient for experimenting 
upon, for it is worthy of remark that the cornea of a young 
animal is more easily inflamed than that of an older one. The 
animal having been narcotized with a mixture of ether and 
chloroform, a small eschar is made in the centre of the 
cornea, with solid nitrate of silver. The animal is then left 
for twenty-four hours, by which time abundant inflammation 
has been excited around the cauterized spot. The entire 
cornea must now be stained with nitrate of silver whilst the 
animal is alive, for the appearances presented if the proto- 
plasm is stained in the living state are very different from 
what are seen when the staining is performed after the animal 
is dead. To stain it properly the animal must be again 
