112 Tue MIcrROoscoPE. 
ians, and it is now agreed upon that the 10 inches should be 
upon the focal plane of the objective to the focal plane of the 
eye-piece. While the focal plane in the eye-piece is about at. 
the diaphragm, that of the objective is back of the posterior 
system of the objective, and varies with every power. In the 
lower powers it may be-as much as an inch, while in the higher 
ones it is reduced to almost nothing. This shows that every 
change of power, either in eye-piece or objective, deviates from 
the standard, and that it is next to impossible to fix one which, 
under all conditions, may be maintained. 
Again,it has been assumed that, as the standard length was 
10 inches, a 1-inch objective and 1-inch eye-piece, each magni- 
fying ten diameters, would give 100 diameters. But the actual 
measurements did not give this result, and from what I have 
stated it can be easily seen why. 
ODE TO THE BACILLUS. 
WM. TOD HELMUTH, M.D. 
Oh, powerful bacillus, 
With wonder how you fill us, 
Every day! 
Wiile medical detectives, 
With powerful objectives, 
Watch your play. 
In epidemic glanders, 
In certain forms of ‘‘ janders,’’ 
You delight. 
£’en to the fifteenth culture, 
Voracious as a vulture, 
You ean bite. 
Koch and Spina, growing splenic, 
O’er your power septicemic, 
Rant and roar. 
Schmidt says when pus grows rotten, 
Only then you are begotten, 
Not before. 
