460 PKACTICAL PHYSIOLOGY 



fatigue and production of lactic acid, and enabled the muscle at rest 

 to remove preformed lactic acid. Irritation or injury of the muscle in 

 any way increased the lactic acid in it. The production of heat rigor 

 in the muscle gave the maximal yield of lactic acid, from 0'4 to 0*5 per 

 cent, zinc lactate according to the time of year. This yield of lactic 

 acid was independent of the previous manipulation, tetanisation, etc., 

 to which the muscle had been subjected. 



CHAPTER XXII. 

 HAEMOLYSIS AND PRECIPITINS. 



A RED blood corpuscle or erythrocyte is usually regarded as consisting of an 

 envelope enclosing haemoglobin and salts of various inorganic bases, of which 

 potassium is predominant in some animals, sodium in others. The interior of 

 the corpuscle is also believed by some to contain a meshwork connected with the 

 envelope and of similar structure. The envelope and meshwork are composed 

 chemically of lipoid substance and protein, and behave physically as a semi- 

 permeable membrane, readily allowing small molecules (such as those of water) 

 to diffuse through but not so readily larger ones, such as those of many inorganic 



Within the envelope the haemoglobin cannot be present in ordinary solution 

 for its concentration is greater than that of a saturated solution of haemoglobin 

 in water or saline solution. The red corpuscle is developed from a cell, but in 

 its metamorphosis most of the cellular properties become lost, the greater part 

 of the protein constituents of the cell changing into haemoglobin. 



In the following experiments some evidence will be obtained to show: 

 1. That the envelope is semi-permeable; 2. That it possesses certain qualities 

 common to it and other cells ; 3. That lipoid substance is an important con- 

 stituent of the envelope. 



It is comparatively easy to study alterations in the permeability of the 

 corpuscular envelope, because, when haemoglobin leaves the corpuscle and 

 passes into the fluid surrounding the corpuscle, this fluid becomes tinged with 

 red : laking or haemolysis is said to have occurred. 



EXPERIMENTS DEPENDING ON THE FACT THAT THE CORPUSCULAR 

 ENVELOPE is SEMI-PERMEABLE IN NATURE. 



EXPERIMENT I. Examine some blood under the microscope (frog's blood 

 is very suitable because of the large size of the corpuscles). Allow some water 

 to run under the cover slip, and at the interface between blood and water 

 note the rapid swelling of the corpuscles followed by their rupture. To 

 another preparation add a 2 per cent, solution of sodium chloride and note 

 that the corpuscles shrink and become irregular in shape. The explanation 



