PREFACE TO THE THIRD EDITION XI 



be decided for each separate case. Every research, 

 which has not been carried out with absolutely 

 unobjectionable technique, delays our arrival at a 

 clear appreciation of the suitability of the methods. 

 There are practically no methods which, on first 

 acquaintance, will lead anyone to good results. 

 Often weeks have to be spent in preliminary 

 studies, before facts are acquired which entitle us to 

 apply the required methods to certain questions. Xo 

 conscientious student would publish these preliminary 

 studies, but would treat them as exercises. Owing 

 to a very extensive experience of my own, I cannot 

 deny that many preliminary studies of this kind have 

 been published. It is only work that is deliberate, 

 and that is based on a complete command of methods, 

 that can lead to satisfactory results. It is, besides, 

 the duty of the clinical worker to thoroughly study 

 each case, and to follow it out to the end. 



As yet, it is too early to criticize the works that 

 have appeared, and I have contented myself merely 

 with summarizing such as have come to my notice. 

 Then the results of recent experimental researches 

 have been referred to. The question of the specificity 

 of the substrates is discussed, and, finally, in the 

 description of the technique, some recent experiences 

 have been considered. 



EMIL ABDERHALDEN. 



November, 1913. 



