82 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



Separation of the serum proteids. — (a) Dilute serum with fifteen times 

 its volume of water. It becomes cloudy owing to the partial precipitation of 

 serum globulin. Add a few drops of 2 per cent, acetic acid ; the precipitate 

 becomes more abundant, but dissolves in excess of the acid. 



(6) Pass a stream of carbonic acid through serum diluted with twenty 

 times its bulk of water. A partial precipitation of serum globulin occurs. 



(c) Saturate some serum with magnesium sulphate by adding crystals of 

 the salt and grinding in a mortar. A precipitate of serum globulin is produced. 



{d) Half saturate the serum with ammonium sulphate by adding to it an 

 equal volume of a saturated solution of the salt. Serum globulin is 

 precipitated. 



(e) Completely saturate the serum with ammonium sulphate by adding 

 crystals of the salt and grinding in a mortar ; a precipitate is produced of 

 both the globulin and the albumin. Filter through a dry filter paper ; the 

 filtrate contains no proteid. 



Hsemoglobin 



6. Direct the spectroscope to the window and carefully focus Fraun- 

 hofer's lines. Note especially D in the yellow, and E, the next well-marked 

 line, in the green. 



7. Direct the spectroscope to a luminous gas flame : these hnes are absent. 

 Place a little sodium chloride in the flame. Notice the bright yellow line in 

 the position of the D line. 



8. Take a series of six test-tubes of about equal size. Fill the first with 

 diluted defibrinated ox-blood (1 part of blood to 31 of water) ; then fill the 

 second tube with the same mixture diluted with an equal bulk of water 

 (1 in 64) ; half fill the third tube with this and fill up the tube with an equal 

 bulk of water (1 in 128), and so on. The sixth tube will contain 1 part of 

 blood to 1,024 of water, and will be nearly colourless. 



9. Into another series of six test-tubes put a few drops of ammonium 

 sulphide ; then pour in some of the contents of each of the first series and 

 warm very gently. 



10. Examine the tubes with the spectroscope and map out on a chart the 

 typical absorption bands of oxyhsemoglobin in the first series, and of (reduced) 

 haemoglobin in the second series. Notice that in the more dilute specimens 

 of haemoglobin the bands are no longer seen, whereas those of oxyhaemoglobin 

 in specimens similarly diluted are still visible. 



11. Take a tube which shows the single band of reduced haemoglobin 

 and shake it with the air ; the bright red colour returns to it, and it shows 

 spectroscopically the two bands of oxyhaemoglobin for a short time. Con- 

 tinue watching the two bands, and note that they fade and are replaced by a 

 single band as reduction again occurs. 



12. Mix a drop of defibrinated rat's blood on a slide with a drop of water, 

 or mount it in a drop of Canada balsam. Examine the crystals of oxyhsemo- 

 globin as they form. 



13. Smear a little blood, obtained by pricking the finger, on a slide and 

 allow it to dry ; cover, and run glacial acetic acid under the cover glass, and 

 boil. Examine microscopically for the dark brown crystals of haemin. 



COAGULATION OF BLOOD 



Microscopic investigation of vertebrate blood shows that it consists 

 of a fluid which holds in suspension large numbers of solid bodies — 

 the red and the white corpuscles and the blood tablets. 



