STUDY OF LIVING CELLS 545 



made from a mixtiire of glucose and copper sulphate is planted on the bottom 

 of the jar. Within an hour, growth will be visible and may procood for 

 several days. 



See Leduc, Etudes de Biophysique, I. Theorie Physico-Chimiqiie de la 

 Vie (1910) : TI. La BioIn(/ie Sijuthetique (1912), 



52. Shell Formation (Rhumbler). 



(1) Mix a" little powdered glass with chloroform and set a drop of the 

 mixture in water. The glass particles gather rapidly round the surface of 

 the drop. 



(2) Repeat the experiment, using fine silver sand dispersed through oil 

 and finally dropped into 70 per cent, alcohol. The movements take place 

 more slowly and the drop requires about three hours to attain equilibrium. 



53. Study of Living Cells. 



[a) Amoeba. The large form may be found in water trickling from a 

 boggy spot. Collect some of the upper layers of ooze from the bottom of the 

 ditch or boggy runlet and leave for a few days in tall jars to allow the ooze to 

 settle. Pipette ofT the surface layer and transfer to a test tube containing 

 clear pond water with some green algae in it. The amoebae will be found on 

 the surface of the ooze. 



Small amoibae may readily be obtained from garden soil by the following 

 method (Goodey, Nature, 1918). Boil some hay or grass in water. Filter. 

 Neutralise filtrate. Take 2-3 gm. of garden earth in each of several Petri 

 dishes and mix with the filtrate from the hay infusion to give a depth of 

 about 2-3 mm. of moist soil. Place in a good light and keep moist. After 

 2-3 days float some cover-slips on the surface of the fluid in the dishes. The 

 amoebae will attach themselves to the under surface of the slips. Remove 

 slips and rinse gently in water in an evaporating basin. Mount in a 

 hanging drop slide with a hair or thread placed below the slip to aid in 

 focussing. 



Examine the slide. Select as large an amoeba as possible and make 

 drawings of it from minute to minute. Place a small drop of N/10 HCl at one 

 side of the preparation and note what happens. Now place 2 drops of 

 N/lO NaOH on the same spot and observe any changes. 



Electrical stimulation. Use a slide with electrodes (Fig. 20) and attach the 

 electrodes through a short-circuiting key to the secondary coil of an induction 

 apparatus. Pull the coil well out, start the interrupter, and open the short- 

 circuiting key for a moment. If no change occurs, gradually push in the coil 

 and try again. Do not expose the amoeba to too strong or too long a shock or 

 it will be disintegrated. 



(6) Blood corpuscles, (i.) Take three test tubes and place in one about 

 5 c.c. of water and in another a similar amount of 0-9 per cent, sodium 

 chloride, and in the third 2 per cent, sodium chloride. Prick the finger 

 with a sterile needle and add the same number of drops of blood to each 

 tube. Shake and examine the tubes (a) as to opacity and (/3) as to depth 

 of colour. Take a drop of the fluid from each and examine under the micro- 

 scope. Measure the diameter of a number of corpuscles and average those 

 from each tube. 



(ii.) Add a drop of fresh blood to a drop of 0-5 per cent, sodium chloride 

 solution on a microscope slide. Place a card on the side of the microscope 

 stage and keeping both eyes open trace the projection of a corpuscle from 

 time to time or measure the diameter. 



(iii.) Experiments similar to those detailed above for amceha may be 

 performed on the leucocytes. 



■ B. 35 



