154 PllEPARATIONS FOR HIGH POWERS. 



the material is thin or can be cut into very small pieces. To a 

 watchglassful of ^^th per cent, chromic-acid solution, made with 

 distilled water, sufficient osmic acid is added to make it smell 

 distinctly, and finally one droj) of formic acid. The material — ■ 

 immediately after death, in the case of an animal — is placed in 

 this for from half-an-hour to two hours, according to size ; that is 

 to say, for as short a time as will ensure thorough penetration of 

 the mixture, which may with advantage be slightly warmed. It is 

 then soaked in several changes of water, to which a little glycerine 

 has been added, and stained in a mixture of equal parts of 

 Kleinenberg's h^ematoxylin and glycerine. The formic acid may 

 be omitted, but delicate nerve-plexuses are not so sharply brought 

 out, and it is then far more difficult to stain. The material 

 should remain in the ha^matoxylin two days, and sliould then be 

 placed in a mixture of equal parts of glycerine and water, and 

 kept lukewarm for a week or longer, until most of the water has 

 evaporated. It may then be mounted whole, or frozen and cut 

 by the process before described, and finally mounted in glycerine 

 jelly. The nuclei amid the protoplasm lining the cells of Ana- 

 charis alsinasiruin may in this way be beautifully demonstrated 

 and compared with a living leaflet exhibiting cyclosis, where the 

 nuclei are indistinguishable from the protoplasm. 



I have tried many methods of preparing delicate tissues for 

 examination with oil-immersion lenses of the highest aperture, but 

 have found these the only ones which give me certain results and 

 enable me to use these lenses with advantage. They are cer- 

 tainly troublesome, and have not the charm of novelty, but enable 

 an aperture of from i '3 to 1 '4 to be effectively employed, and I 

 think will be found successful in direct proportion to the care 

 used in carrying them out. 



Fumigation is said to have originated with Acron, a physician 

 of Agrigentum, who is said to have caused great fires to be 

 lighted, and aromatics to be thrown into them to purify the air, 

 and thus to have stopped the plague of Athens and other places 

 in Greece about 473 b.c. 



