ANIMAL FLUIDS AND TISSUES. 433 



Hcemoglobin is the chief constituent of the red corpuscles, and the 

 substance which carries oxygen to the various tissues, as described in 

 connection with the consideration of the process of respiration in the 

 previous chapter. 



Experiment 64. Pour some freshly drawn venous blood into four volumes of 

 a saturated solution of sodium sulphate contained in a vessel which stands in 

 ice ; mix and set aside for several hours ; no coagulation occurs and the cor- 

 puscles settle to the bottom of the vessel. Pour off the supernatant liquid, 

 collect the sediment on a filter, and wash it first with cold solution of sodium 

 sulphate and then with water. 



Prepare haemoglobin from these corpuscles as follows : agitate the collected 

 mass violently with small quantities of ether until the corpuscles are nearly 

 dissolved ; allow the liquid to settle, filter, render the filtrate slightly acid with 

 acetic acid, and add alcohol as long as the precipitate first formed continues to 

 dissolve ; cool the red solution to C. (32 F.) for several hours, when crystals 

 of haemoglobin will form ; collect these on a filter and wash with an ice-cold 

 mixture of alcohol and water. 



Examination of blood-stains. Blood-stains may be recognized, 

 after having been washed off with as little water as possible, by the 

 following methods : 



1. Examine the reddish fluid under the microscope for blood cor- 

 puscles. 



2. Evaporate a drop of the fluid on a microscope slide with a 

 minute fragment of sodium chloride, cover with a cover-glass, allow 

 a drop of glacial acetic acid to enter from the side and warm gently; 

 abundant crops of hsemin crystals are seen under the microscope 

 after cooling. 



3. Add a drop of the fluid to some freshly prepared tincture of 

 guaiacum in a test-tube and float on the surface of an ethereal solu- 

 tion of hydrogen dioxide; a blue ring forms at the junction of the 

 ethereal solution and the guaiacum. (Blood is, however, not the only 

 substance showing this reaction. 



4. The spectroscope shows bands characteristic of haemoglobin. 



Chyle is a white, creamy liquid, of a strongly alkaline reaction, 

 having in common with blood the property of coagulating (upon 

 leaving the organism) into white fibrin and turbid serum. The com- 

 position of chyle differs according to the state of digestion ; it contains : 



During full digestion. During fasting. 



Water 91.8 per cent. 96.80 per cent. 



Fibrin 0.2 " 0.09 



Proteids 3.5 " 2.30 " 



Fats 3.3 0.04 



Extractives . . . .0.4 " 0.28 



Salts 0.8 0.49 " 



28 



