THE DRAWING OF MICROSCOPIC OBJECTS. 303 



the cone of rays reaching the eye ; on the other hand, the endeavour 

 to depict the objects as they appear in nature, and yet combined 

 with different sectional views; and again, the habit of keeping 

 oneself at the distance of distinct vision with the naked eye or 

 with transmitted light; and finally, the difficulty or rather im- 

 possibility of producing the conditions of microscopic vision for the 

 naked eye, we are unable to suggest how all these opposing 

 conditions can be reconciled in a satisfactory manner. The 

 natural reproduction of the microscopic image in a photographically 

 true, or even in a rationally diagrammatic manner, is and remains 

 conceivable only for a definite focal adjustment ; with solid figures 

 it is an impossibility. 



For some years pkotomicrographic representations of objects, with 

 drawings of them in juxtaposition, have attained a considerable 

 importance. Preparations, the production of which involves great 

 difficulties, may in this way be rendered permanent to a certain 

 extent, and thus serve for subsequent investigations from new 

 points of view, whilst the draughtsman accurately reproduces 

 only those special points which engage his attention. This 

 advantage of the photomicrographic process has, however, been 

 felt rather by the zoologist than the botanist. Moreover, since the 

 manipulation of the photomicrographic apparatus presupposes a 

 knowledge of the photographic processes on which subject 

 special treatises have in recent years appeared we must refer 

 those of our readers who would learn more of this branch of 

 technical microscopy to the special treatises. 1 



1 The most complete work upon this subject is " Die Photographic als Hiilfs- 

 mittel mikroskopischer For seining," translated from the French work of Dr. A. 

 Moitessier, with numerous additions by Dr. B. Benecke (Brunswick, 1868). 

 Cf. also Gerlach's book with the same title (Leipzig, 1863). 



