191 



equal parts of toluene and paraffin for 24 hours and then 

 in paraffin for 24- hours. 



The paraffin can be dissolved from the sections by 

 means of xylol or turpentine. The sections are then placed 

 in absolute alcohol and finally transferred to 10% alcohol, 

 in which they may be kept for any length of time and are 

 now ready for staining, 



Paraffin sections sometimes tend to curl or become 

 folded. This difficulty can be readiiy overcome by plac- 

 ing the sections in a Petri dish containing tepid water. 

 This must not be so warm as to melt the paraffin. The 

 dish may be kept on an iron plate which is heated gently 

 at one end. The sections spread out on the surface of the 

 warm water. They can be received on strips of paper and 

 transferred to a glass-slide or cover-glass which is covered 

 with a film of albumin. The section is then dried with a 

 piece of paper and caused to adhere by slightly warming 

 the glass slide. It can then be stained in the usual man- 

 ner. The method is very convenient in working with very 

 thin sections or with very delicate tissues. (BORREL). 



Staining of Sections. The presence of organisms 

 in sections of tissues is sometimes very difficult to demon- 

 strate although they may be easily shown to be present 

 in ordinary streak cover-glass preparations. This is fre- 

 quently due to the absence of any sharp means of differ- 

 entiating the organism from the surrounding tissue. In 

 many cases, however, a sharp differentiation can be ob- 

 tained by double staining either by Gram's method, or, as 

 in the case of leprosy and tuberculosis, by the Triplication 

 of the usual process for staining these bacilli. 



Simple stain. The student should begin with c ec- 

 lions of the spleen, kidney and liver of a guinea-pig which 

 died of anthrax. The sections are transferred by means 

 of a needle to the dilute anilin .dye, as fuchsine or gentian 

 violet and are allowed to remain there for 10 to 30 

 minutes. They are then transferred to water slightly acid- 

 ulated with acetic acid, or to very dilute alcohol. This is 



