2D0 THE AMERICAN MONTHLY [Sept 



workers;, unless a certain auioiiut of their time is devote il 

 to experimentation. A person, who lias obtained fairly 

 ■successful results with his older methods, is loath to for- 

 !-ake them, especially if his first few attempts wiih the 

 new are failures. Each investigator may have certain 

 laboratory conveniences ; reagents of the best quality and 

 dyes that have been well tested, all of which will enable 

 him to obtain results much superior to his less fortunate 

 colleague. It is ditticult, therefore, to work successfully 

 unless details are carefully attended to, and the reasons 

 for the various steps understood. The methods following 

 have been well tested, and have been attended with uni- 

 formly good results, which in some cases, it is believed, 

 would have ended in failure with the older methods. 



FIXATION. 



The fixation of pathological tissues, with strong alcohol 

 for histological study, is very commonly employed for 

 the double purpose of killing at once any microorganism 

 that may be present and at the same time to preserve 

 the structure of the part. With many tissues this 

 caused a too rapid withdrawal of the contained water or 

 lymph, so that the specimen becomes hard and gives 

 unsatisfactory results when it conies to the cutting pro- 

 cess. 



Some experiments with different reagents, upon known 

 pathological material, were of service in formulating a 

 mixture, which obviated the defects of strong alcohol 

 when used alone. This mixture, while quickly killing 

 the bacteria, also preserves most faithfully the histologi- 

 cal structure. Various solutions of formalin, including 

 the undiluted, were employed, and gave good results, 

 particularly the presentation of the bacteria, after the 

 usual staining methods. The tissues were more or less 

 swollen by the weaker solutions, in marked contrast to 

 the contraction caused by alcohol. Various combinations 



