178 PHYSIOLOGY. 



this envelope. Hedin has shown that the red corpuscles are very 

 permeable to aldehydes, ketones and alcohols. 



The action of certain organic substances is of considerable 

 importance. Thus, bile and the alkaline salts of the biliary acids 

 have the power to dissolve and destroy the red corpuscles with 

 phenomena which resemble those produced by the action of chloro- 

 form. Urea in solution and excess of alkali also destroys them. 



The lowering of osmotic pressure in the plasma by water will 

 make the blood laky, an act of haemotysis, because an excess of water 

 lowers the osmotic pressure outside the corpuscle; then the water 

 enters the corpuscles, discharges and dissolves the hemoglobin. 



The red corpuscles comport themselves in saline solutions as an 

 element with a semi-permeable envelope containing a liquid. 



For each sodium chloride solution there is such a degree of con- 

 traction that the red corpuscles remain the same as in the plasma. 

 This is called an isotonic solution, and its osmotic pressure is the 

 same as that of the plasma. If the water in the sodium chloride 

 solution is proportionately increased, the blood-corpuscles absorb a 

 part and swell. Here the osmotic pressure of the sodium chloride 

 solution is lower than that of the plasma, and is called a hypotonic 

 solution. When the osmotic pressure is higher than that of the 

 plasma, then the red corpuscle gives out its water until the osmotic 

 pressure of the cell contents is equal to the osmotic pressure of the 

 solution. This is called a hypertonic solution. 



The percentage of NaCl necessary to generate such a solution 

 is, for frogs' blood, 0.65 per cent.; for blood of man, 0.95 per cent. 



Hsemolysins. Laky blood may also be produced upon the injec- 

 tion of the blood-serum of one animal into the blood of another kind 

 of animal, the serum having the power to destroy the red corpuscles. 

 The term "globulicidal action" covers this property of the serum. 



But the term "globulicidal action" has been replaced by the 

 term haemolysis. This is not due to differences in osmotic pressure, 

 but to a haamolysin in the blood which is composed of two bodies, 

 amboceptor and complement or alexin. The microbe of tetanus 

 generates. a tetanolysin. Snake venoms set free the haemoglobin in 

 red corpuscles. The action of foreign serum is not limited to an 

 action only on the red corpuscles, for it may attack nerve and other 

 cells. 0.04 cubic centimeter of serum of certain Italian eels by the 

 vein kills the rabbit, with apparently an action on the vasomotor and 

 respiratory centers. Dilutions of serum of certain Italian eels 1 to 

 15,000 or to 20,000 produces haemolysis of the red corpuscles in other 



