The Minute Anatomy of Tivo Cases of Cancer. 109 
balsam angle 110°, is, as before stated, made on that plan, but not 
strictly according to what tbe figure represents, for that is an 
extreme case, to help apprehension, and the refraction is all ac- 
complished by the three inner systems. In this f (of the table) 
the front lens is thin and has considerable action to bend the rays 
towards the axis, and the objective has a good range of working 
distance. To get the highest practical balsam-angle on this plan, 
of course the action of the two lenses at the front of the objective 
is so apportioned between the two as to favour convenience in use 
as well as efficiency. In this diagram, moreover, the three inner 
systems are identical with those of Mr. Wenham’s •§■, as he repre- 
sented them, and I thus limited the case, and all the question, to 
the added fourth lens. Therein was the reason his diagram was 
copied. That part he would not impeach. I never used such a 
set of combinations. Would not select it as choice for any purpose. 
In conclusion, one point may as well be noted, as of some 
practical importance, viz. that with a water immersion objective in 
use, a water immersion condenser of the same balsam angle will give 
closely the full dimension of illuminating pencil that can reach the 
water-immersed objective above, and be transmitted by it. About 
125° balsam angle, for the condenser would cover all cases of use 
of water immersion objectives. I pointedly suggested this in my 
first communication. 
Boston, July 23, 1S72. 
VI. — The Minute Anatomy of Two Cases of Cancer. 
By Assist.-Surgeon J. J. Woodward. 
Plate XXIX., from the Author’s Photographs. 
Opportunities for the study of the histology of morbid growths 
frequently occur at the Army Medical Museum. Specimens are 
sent, not merely by medical officers of the army, but also by civil 
practitioners. It is often possible to examine these growths while 
quite fresh, and thus to make observations which aid in the 
interpretation of the appearances found in those which are not 
received until they have been hardened by immersion in alcohol or 
other reagents. By methods described in former reports, it is 
possible to preserve thin sections of very many of these growths in 
a permanent form for examination with the microscope, and a large 
collection of such preparations has already been formed. 
These preparations are frequently studied by medical officers 
