1894.] 3IICR0SC0PICAL JOURNAL. 267 



are excellent, but not permanent. ... To observe the 

 cells of Purkinji select a sheep's heart. . . . By super- 

 ficial incisions circumscribe a square of endocardium, and 

 remove it with a razor, taking great care not to trench to 

 the slightest degree upon the myocardium. Divide the 

 piece in two ; carefully spread one portion face upward 

 on a slide ; if few fibres of the myocardium remain, stain 

 with picro-carmine and mount in glycerine, but if they 

 are in great numbers and mask the fibres of Purkinji, 

 remove them by brush and forceps before proceeding 

 further. The second portion being spread on the slide, 

 add a drop of 40 per cent potash solution, and cover ; to 

 dissociate the cells forming the fibres of Purkinji press 

 on the cover with a needle. 



To make ti'cinvers sections of the fibres. — Picric acid and 

 ammonia bichromate answer very well to fix the tissue. 

 Harden by alcohol, imbed in gum. Sections made after 

 the action of the bichromate, should be stained by hasma- 

 toxylin and eosine, and mounted in balsam ; after picric 

 acid, stain in picro-carmine and mount in formic acid 

 glycerine. 



The e7idocardiuni and the valves. — The former may be 

 well studied in sections made perpendicularly to the in- 

 ternal face of the heart. Fix by picric acid, harden in 

 alcohol, imbed in gum ; stain by picro-carmine, and 

 mount in acid glycerine. 



To see the endocardial endotheliufn select the heart of a 

 rat or of a rabbit. Into a vein inject a solution of silver 

 nitrate 1 to 300; until the liquid returns through the ar- 

 teries. Wash the internal surface of the heart with the 

 silver salt, open it in a vessel full of distilled water and 

 expose to direct sun light. With a razor, cutting paralel 

 with the surface, remove a fragment of the endocardium 

 and spread it on a slide with the inner face upward. 

 Stain with alum carmine, wash, dehydrate by absolute 

 alcohol, clear by clove oil and mount in balsam, 



