678 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
are necessary in bacteriological research, and in testing blood-corpuscles 
to determine, for instance, whether they are of human blood or not. 
A local paper recently told of a Boston physician who examined the 
tubercle bacillus with a powerful glass that magnified 900 times. 
Bidiculous ! You can’t see the consumption bacillus with an objective 
that magnifies less than 1200 times. England is the great rival of this 
country in Microscope-making. France and Germany are behind. I 
suppose that sometime an objective will be made that will magnify 10,000 
times, but it will be a much more difficult task than the making of a 
telescope glass five feet in diameter.’ 
“ While no one will deny that Bobert B. Tolies was one of the 
greatest lens-makers that the world ever saw, there are a great many 
who would hesitate to place him above his great contemporary and 
teacher, Charles A. Spencer, of Canastota, N.Y. Neither of them, 
however, ever ‘made an object-glass that magnified 7500 times.’ To 
do this would require the manufacture of an objective with a focal 
length of 1/750 in., which, it is needless to say, has never yet been 
attempted. Nobert’s ‘nineteenth band’ contains 112,595 lines to the 
inch (estimating the Paris line at 0* 088 • 813 * 783 in.). The Tolies 
‘ seventy-fifth ’ was not ‘1/75 in. in diameter,’ but the combination 
had a theoretical focal length of 1/75 in. When used with a 1-in. 
ocular and with a 10-in. tube-length the combination would give an 
amplifying power of about 7500. 
‘Objectives that magnify 5000 times are rare.’ We should say so 
— and likely to remain so, since to make one would require the con- 
struction of a combination with a theoretical focal length of 1/500 in. 
The balance of this sentence shows that Mr. Dalton (or the reporter) 
confuses the Microscope (here the combination of eye-piece and objective) 
with the objective alone. 
The statement regarding the visibility of bacillus tuberculi is not 
less misleading than the balance of the farrago. Bacillus tuberculi can 
easily be seen and recognized with a 1/5-in. objective and a 2-in. ocular, 
or, roughly, with an amplification of 250. With twice this amplifica- 
tion (i. e. 500) it becomes a very conspicuous object. In fact, the 
writer rarely uses amplification over 500 in making examinations for 
tubercle bacilli, his favourite combination being a 2-in. ocular and 
1/10-in. objective.” 
j8. Technique.* 
(1) Collecting Objects, including Culture Processes. 
Preparation of Nutrient Media. f — Dr. N. K. Schultz finds that 
really good bouillon agar and gelatin can be obtained by attending to 
several details which in practice are highly important. He recommends 
that the precipitates formed during the preparation of the medium 
should be removed separately, because each precipitate has its own 
special properties. The reaction of the medium should be determined 
by titration since neutralization cannot be accurately ascertained by 
* This subdivision contains (1) Collecting Objects, including Culture Pro- 
cesses; (2) Preparing Objects; (8) Cutting, including Imbedding and Microtomes. 
(4) Staining and Injecting: (5) Mounting, including slides, preservative fluids, &c. ; 
(6) Miscellaneous. f Centralbl. f. Bakteriol. u. Parasitenk., x. (1891) pp. 52-64. 
