1898J MICROSCOPICAL JOURNAL. 23 



Dahlia as a Stain for Bacteria in Sections Cut by the 

 Collodion Method. 



Probably the greatest diflBculties have been found in the 

 staining of the imbedding medium or in the albumen fixa- 

 tive. They usually obscure both the tissue elements and 

 the bacteria. Unless the sections are cut in parafiin and 

 not fastened to the slide by these common fixatives the 

 bacteria are not brought out. With loose or fragile tis- 

 sues there is great danger of tearing or of losing parts of 

 them during stainingand dehydrating. Although parafiin 

 is commonly used, collodion is more often employed. 

 The rule in normal histology is to fasten the sections to 

 the slide. In pathological histology, they are not, for 

 the reasons mentioned, ordinarily fastened. The need 

 of having an absolutely perfect section from a pathologi- 

 cal tissue, especially for diagnosis, is even greater than is 

 the case when sections of normal tissues are being made. 

 The loss of a very small bit from the section may cause 

 an entirely erroneous interpretation. By the use of col- 

 lodion as the imbedding medium this danger is eliminat- 

 ed. The method is simpler and the sections are fastened 

 to the slide by collodion or an albumen fixative. 



Collodion takes most of the aniline dyes and gives up 

 the stain only vyhen treated with a decolorizing agent 

 sufliciently strong to decolorize the tissue at the same 

 time. In the case of paraffin sections which have been 

 fastened to the slide with collodion or albumen fixative, 

 or both, besides the disadvantage of using a process 

 which takes a longer time, we meet the same difficulty 

 that we did in the collodion method. The fixative takes 

 the stain and obscures the preparation quite as much as 

 does the imbedding collodion. 



Both the collodion and the parafiin methods have ad- 

 vantages. In pathological histology I prefer collodion to 

 parafl&n. The whole process of sectioning by the oil-col- 



