DECOMPOSING BLOOD, ETC. 235 



direction, then the blotting-paper was shifted. Sometimes two or 

 three httle strips were used to divert the flow, so that the 

 minute free organisms should not be withdrawn out of the ring. 

 After the tannin had acted for five minutes, a drop of water was 

 placed at the edge, and this sucked through, repeating its use 

 as often as appeared necessary. When the tannin solution had 

 been removed and the washing made effective, a drop of a 

 saturated solution of sulphate of iron with lo grs. of citric acid 

 to the ounce of solution were allowed to act for five minutes, 

 and then washed out by water as described for the tannin ; then 

 the mounting medium was placed at the edge of the cover, and 

 by means of absorbent paper made to take the place of the 

 water. A solution of chrysoidine was sometimes employed after 

 the water washing, if the sharpness of the outline seemed defi- 

 cient in the objects. 



The same method was adopted when using any of the ordinary 

 aniline stains, besides employing the usual plan of drying the 

 material on the cover, then using the difierent fixing or staining 

 materials, and washing from a pipette, or by soaking, allowing the 

 cover to float on the water. Some of the minute dirt-particles I 

 found were sucked out to the advantage of the mount, and no 

 doubt some of the loose organisms went with the dirt. It took 

 some time to accomplish before the cover could be fixed down by 

 the usual Hollis' glue, but I found the plan under the circum- 

 stances to yield me the best effects. The tannin, as is well known, 

 has an immediate action on such parts of the organism as the 

 cilia and flagellum, and also tends to fix the soft plasm ; the iron 

 solution, after its action for a short time, stains both parts of the 

 organism, showing a pale grey tint in the flagella, which readily 

 catches the eye when using the microscope. Logwood solution 

 and iron were also tried, and likewise reversing the solution of 

 tannin and iron by allowing the iron to act first, but preference 

 was given to using the tannin first. All this detail will no doubt 

 be sadly wearying to those who are far more efficient workers than 

 myself; they will therefore excuse it, I trust, in favour of those 

 less experienced than themselves. 



The foregoing will show that in the original material supplied 

 to me, I had; although in an early stage of putrefaction, what 



