and Laboratory Methods. 1985 



are placed for five minutes in a 1 per cent, watery solution of iodine, rinsed and 

 mounted in water. This procedure stains the nucleoli, nuclei, protoplasm, and 

 cell walls a beautiful yellow or brown. 



The beginner is likely to be in doubt over the protoplasm of the cell. An 

 experiment in plasmolysis will give him a better idea of its nature. Two or three 

 of the fixed pieces are treated for five minutes with an SO per cent, solution of 

 alcohol and then stained for three minutes in a 1 per cent, watery solution of 

 methyl violet, rinsed and mounted in water. This gives a beautiful violet prepa- 

 ration showing not only the cell wall, nucleus, nucleolus, but also the protoplasm as 

 a distinct mass with a clear space between it and the cell wall. 



A beautiful double stain may be secured as follows : Two or three pieces of 

 the fixed membrane are immersed in Delafield's haematoxylin for ten minutes. 

 They are then rinsed in water to free them from an excess of stain. The haema- 

 toxylin is then removed from all parts of the cell except the nucleus by the fol- 

 lowing mixture : Hydrochloric acid, ten drops ; water, 100 c. c. The stained 

 specimens should lie in this till they fade to a salmon pink in color. They are 

 then to be floated on ordinary water till they assume a light blue color. Now 

 they are ready for a 1 per cent, watery solution of eosin for one-half minute, rinsed 

 and mounted in water. The preparation should show the nucleus stained a rich 

 blue, and the other structures an attractive pink. 



Satisfactory work on the animal cell may be secured by the use of smears of 

 frog's or toad's blood on glass slides. The toad is suggested as it is more easily 

 secured than the frog and is every whit as good. The animal is anaesthetized with 

 chloroform. Its chest cavity is exposed and the apex of the heart is snipped off. 

 The blood spreads into the pleural cavity. A swab may be made by twisting about 

 the end of a toothpick a bit of surgical cotton half the size of a pea. Each member 

 of the class makes his own smears by a light stroke with the above swab. Blood 

 side up, the slides are passed through the Bunsen or alcohol flame three times. 

 The smear is then ready for the stain. 



A drop or two of Delafield's haematoxylin is placed on the blood spot and 

 allowed to act ten minutes. The slide is then held under the flow of a tap till 

 all free stain is washed off. There is no danger of washing off the smear. A 

 drop of a 1 per cent, watery solution of eosin is flooded over the smear for one-half 

 minute and then as before it is held in the flow of the tap water till no stain 

 washes away. Glycerine is added and a cover glass. 



In a successful mount, the oval blood cells show a most beautiful contrast 

 stain. The nucleus is a deep blue and the protoplasm, without the nucleus, a 

 bright pink. The fact that haematoxylin is a nucleoplasmic stain and eosin a 

 cytoplasmic one may be emphasized from the very start. 



Slips bearing directions for each step of the above operations should be in 

 the hands of each student at the beginning of the laboratory period. 

 Waynesburg College. JACOB F. BuCHER. 



