110 The Minute Anatomy of Two Cases of Cancer. 
and others who visit the Museum for that purpose, hut they would 
be rendered more generally useful if it were practicable to publish 
from time to time brief descriptions of the more important cases, 
accompanied by suitable illustrations. 
The usual methods of representing such microscopical prepara- 
tions by etchings on copper, lithographs, or woodcuts, are open to 
many objections. Especially it may be indicated that the produc- 
tion of the drawings which must serve as the basis of such 
representations is laborious, and consumes too much valuable time 
if the investigator himself endeavours to make them ; and if the 
work is entrusted to a professional artist the essential features of the 
image are very generally imperfectly shown, or altogether mis- 
represent the original. Even if the microscopist himself has the 
leisure and the skill to make his own drawings, the finished work 
will too often represent rather his theoretical views than the severe 
facts of nature, for in any case the artist finds it impossible to 
represent all that he sees in the microscope, and only attempts to 
reproduce so much as he conceives to be of importance. 
Much more truthful representations can now be made by the 
process of Photo-micrography as improved by my experiments ; 
but the cost of making silver prints, the fact that they are not 
permanent, and the circumstance that they require to be mounted 
on tolerably stiff cardboard, prevent them from being generally 
available as hook illustrations, especially where editions of several 
hundred copies or more are desired. Under these circumstances 
I note with pleasure the rapid improvements lately made in the 
direction of photo-mechanical processes of various kinds, having for 
their object the reproduction of photographic negatives in inks of a 
permanent character. These processes are indeed as yet far from 
perfect, but several of them have already reached such a degree of 
excellence as to be very suitable for the reproduction of photo- 
graphic negatives of microscopical images. 
In the United States two such methods may be said to be in 
successful operation, viz. the Woodbury process, and the Alber- 
type process. A detailed account of these processes would be out 
of place here, but a few brief remarks are required. 
The Woodbury method consists essentially in the production 
from the negative, by the action of light, of a relief surface of gela- 
tine, from which a metal “ intaglio ” is produced by pressure. In 
this a series of gelatine films coloured by any suitable permanent 
pigment are formed by mechanical means, and these constitute the 
prints. Like silver pictures the Woodbury prints require to be 
mounted on sheets of cardboard or stiff paper, and this of course 
adds to the expense. Moreover, if the mount is thick it is ill 
adapted to binding. Of late, however, films of great flexibility 
have been produced, which are supported on mounts not much 
