FROM THE 

 PREFACE TO THE FIRST EDITION. 



Doubt, honestly arrived at and acknowledged, is better than apparent 

 certainty without a statement of those things upon which it depends. 



FOR years my brother, J. F. Lehmann, the publisher 

 in Munich, has requested me to furnish him for his 

 "Medical Atlases" one which would simplify bacterio- 

 logic diagnosis. After I had long refused to undertake 

 the vast labor which this would necessitate, a fortunate 

 circumstance in the summer of 1894 led me to accept the 

 plan. I discovered in Dr. R. Neumann, who was working 

 in bacteriology in my institute, so excellent a talent for 

 drawing and painting that I proposed to him that he 

 undertake the work with me. Whether we have solved 

 the problem remains for the critics to decide. It seems 

 to me that the plates, painted by Dr. Neumann with un- 

 tiring zeal under my continual supervision, and carefully 

 reproduced by the lithographer Fr. Reichhold in Munich, 

 are a useful addition to our means of teaching. With few 

 exceptions, the reproduction leaves little to be desired. At 

 least, we have had the satisfaction of finding the pictures of 

 great advantage in our own work and in that of numerous 

 gentlemen working in our institute. We carried out many 

 investigations regarding the method of illustrating before 

 selecting the one employed, which may be considered as 

 almost entirely satisfactory. 



At the present time, when, properly, photography is so 

 much used for the objective representation of objects in the 

 natural sciences, especially those of bacteriology, many will 



