liLOOl) 



549 



61. Model to Illustrate some Phases of Urine Formation. (Fischer and 

 MiicLaughliii.) 



Prepare some cujjs of .sodium stearate l)y ])Ourin<f the liot stearate sohitioii 

 (1/10 molar) into a moidd consisting of one beaker (120 c.c.) suspended within 

 another similarly shaped (350 c.c). A cup is supported on a filtration disc 

 in a filter funnel whose stem enters the mouth of a graduated cylinder. 

 Another cylinder (gas jar) or bottle inverted may be used as a constant 

 level device. Fill the cup and the gas jar with the solution. Invert the full 

 jar and suspend it vertically so that its mouth just dips below the surface 

 of the fluid in the cup. From time to time measure the fluid in the lower 

 graduated cylinder, say every hour. 



Try the following solutions : (a) water (3-6 hours), (6) molar sodium 

 oleate (24 hours), (c) NaCl 1/8 M., 1/4 M., and 1/1 M. (3-6 hours), [d) 1/8 M. 

 CaCl.2 (1-4 hours), (e) 1/8 M. NH^Cl (7 hours). 



Note increased flow with (c) and {d) ; initial increase and final decrease 

 of flow with (e) and total inhibition W'ith [h). Test, in each case, the per- 

 fusion fluid, the perfusate and the cup, with phenolphthalein. How do 

 you account for your results I Test the perfusates for fatty acids. Why 

 does pure water dissolve out more of the acid than do the salt solutions ? 



62. Specific Gravity of Blood. 



Make up a series of solutions of sodium sulphate or of mixtures of benzene 

 and chloroform to give specific gravities ranging from 1-04 to 1-07. Puncture 

 the finger (use a sterile blood lancet, i.e. one with a flat .sharp edge and not a 

 sewing needle) and allow a drop of blood to fall into each tube of liquid. 

 f)ee that the drop pierces the surface of the liquid. Note in which tube the blood 

 drop remains suspended or sinks verj' slowly. The specific gravity of the fluid 

 in that tube is equal to or almost equal to the specific gravity of the blood. 



Preparation of (a) Sodium sulphate solutions. 



(6) Benzene and chloroform mixture. Make a mixture of chloroform and 

 benzene of specific gravity 1-07. Stir in benzene to get the smaller values of 

 the specific gravity. 



Another method. Place the mixture of chloroform and benzene with a 

 specific gravity of 1 -07 in a urinometer tube. Drop one drop of blood from the 

 finger into the tube. If the drop floats add benzene and stir with a glass rod. 

 Continue addinti benzene and stirring till the drop of blood neither floats nor 

 sinks. The specific gravity of this mixture taken with a hydrometer is the 

 specific gravity of the blood under test. 



63. Haemolysis (see also Experiments 53 (6) and 64). 



(i.) Mix a drop of your blood with a drop of distilled water on an uncovered 

 microscope slide and observe. The corpuscles swell up, burst and liberate 

 haemoglobin. 



(ii.) Repeat, using instead of water some fat solvent like ether, chloroform etc. 



(iii.) Repeat, using a capillary active substance in dilute solution, e.g. bile 

 salts, saponin, etc. 



64. Estimation of the Fragility of Human Red Blood Corpuscles. 

 Twelve clean small test tubes (4 x ^ in.) are placed in a row in a rack and 



numbered from left to right 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15 and 14. 



