Journal of Applied Microscopy. 465 



A Good Killing Fluid. 



After experimenting with a large number of the various killing fluids which 

 have been recommended from time to time, I have always come back to the 

 chrom-acetic acid mixture as giving the most reliable results. Chrom-acetic acid 

 is an excellent fluid for nuclear preservation, especially when the amount of acetic 

 acid is relatively large. It is not so satisfactory for preserving the cytoplasmic 

 structures. In finding a substitute for chromic acid, I have followed up the 

 results of Tellyesniczky^, who recommends a mixture of acetic acid and potassium 

 bichromate for preserving the structure of animal cells. After trying several 

 strengths, I believe the following to be the best combination for plant cells : 

 potassium bichromate, 0.8 gram; glacial acetic acid, 0.5 cubic centimeter; water, 

 99.0 cubic centimeters. This fluid gives excellent results. The objects do not 

 become discolored, but remain clear. The nucleus is nearly, if not altogether, as 

 well preserved as in chrom-acetic acid, while the cytoplasmic structures are usually 

 more satisfactory. Small pieces of tissue, from a half to three-quarters of a centimeter 

 long, should stay in the fluid from twelve to twenty-four hours. The sections take 

 a good stain and are especially appropriate for anilin-safranin and gentian-violet, 

 and Haidenhain's iron-alum-haematoxylin. Acetic-potassium-bichromate deserves 

 a careful trial, as it will probably prove more satisfactory than chrom-acetic acid. 



Ohio State University. JOHN H. SCHAFFNER. 



A Modification of Van Gehuchten's Methelyn Blue Method. 



The following is a modification of Van Gehuchten's methelyn-blue method 

 as given by Prof. Lee. Excellent re'sults have been obtained by it in the study 

 of the brain of the fish, especially in the study of the cell structure. 



Fish were killed by cutting the spinal cord just back of the medulla. The 

 large blood vessels should be cut while the heart still beats, that as much blood 

 as possible may be drained away from the brain. The blood corpuscles 

 give a very deceptive appearance when stained in the vessels penetrating the 

 brain. Before placing the brain in alcohol, it is well to cut away as much of the 

 head as possible without injuring the brain. This allows the alcohol to pene- 

 trate uniformly and prevents the brain from becoming colored, as it does when 

 the surrounding tissue is not removed. The head may then be placed in 35, 

 50, 70, 85, and 95 per cent, alcohols for from twelve to sixteen hours in each 

 grade. The brain is now easily removed from the head and placed in absolute 

 alcohol for four or five hours. It should not show any shriveled appearance, as 

 it will if fixed in a high grade of alcohol at once. It is now put in chloroform until 

 it sinks, when it may be put in the paraffin bath, and imbedded. Cut with a 

 sliding microtome, the sections alternating 15 and 20 yu, since some points are 

 more easily made out in the 15 /^ sections, while others are best found in those 

 20 }x thick. Fix by the distilled water method. Remove the paraffin with 



lUeber die Fixirangs — (Hartungs) — Fliissigkeiten. Archiv. f. Mikr. Anat. 52: 202-247, i{ 



