206 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
a right angle upon the projected paper placed in a horizontal position. 
The Oberhauser camera is attached to the tube of the Microscope at the 
ocular end, without any trouble or loss of time. With but one exception 
this camera is perfect ; it has a deficiency in one particular. When the 
microscopic picture is twice reflected it then loses considerably in accu- 
racy, that is, in its clearness and exactness. This is especially so in the 
use of higher powers, oil-immersions, &c. By the most concentrated 
light only can the special and superficial contour of the microscopic 
picture be best produced. 
The practical and most applied drawing apparatus in microscopical 
work is the camera lucida. The object and the paper are £een with the 
one eye, and at the same time the picture is reflected into the eye by 
means of the mirror or prism. As the picture is seen upon the paper 
beside the Microscope, its contour can be reproduced upon the paper 
with the point of a pencil, and that too with mathematical and scientific 
exactness ; but he who has by practice learned to look into the Micro- 
scope with one eye and to hold the other eye open at the same time, may 
get along even without the use of a camera lucida if he gazes with one 
eye into the Microscope and with the other eye at a piece of paper lying 
beside the Microscope. In a few moments the observer will find the 
object projected upon the paper and will thus be able to sketch the 
outlines with comparative ease and exactness. 
In the execution of the drawing of the microscopic object it is best 
to use strong paper — Bristol paper or Bristol board — and the paper 
should be either pale-yellow, pale-green, or white and slightly shaded. 
It is also advisable to have the paper fastened upon a smooth board. 
First use a soft and finely sharpened black pencil in order to secure the 
outlines and the contour of the picture. It should be slightly shaded, 
without pressure. Then, with bread-crumbs, rub most of it out again. 
After that, with a heavy pencil, retrace the outlines of the first drawing 
again, using the prism for comparison and exactness. This moment is 
the proper time to do the shading, if such is required, and this can easily 
be done with the point of a pencil and a rubber, or, still better, with 
charcoal and soft cloth. For drawing a picture with colours, water 
colours are most commonly used ; after them coloured lead pencils, oil 
colours, and pastel crayon. I wish here to call special attention to 
this fact, that in shading it is advisable to shade off the uncoloured 
parts first with black ; particular care must be taken that the shading 
does not extend into the coloured field. It is also decidedly recom- 
mended to use a variety of colours, especially in the drawing of 
very minute objects such as endothelium and epithelium cells, fibrous 
and connective tissue cells, blood and lymphoid cells. In drawing a 
whole slide, or only a part of it, it is sometimes desirable to use a variety 
of colours. Not only will it make a drawing more elaborate, but 
decidedly more comprehensive and instructive. 
Virchow, the most expert pathologist of the nineteenth century, has 
said that he would not give “ ein Pfennig ” for illustrations, drawings, 
or sketches that were not correct and exact, because in every instance it 
would convey a false impression. Besides this, Virchow has said that 
all lectures, demonstrations, original articles of any kind, should be 
accompanied by first-class drawings or illustrations. 
