The Blood. 29 



The number of corpuscles in the blood is approximately 

 determined either by the method of Gowers, or Malassex. 

 The principle on which these are based is the same— a 

 known quantity of blood is diluted with a known bulk of 

 artificial serum and accurately mixed ; of this a small drop 

 is placed in a counting-chamber, which is ruled into squares, 

 and examined under the microscope. The blood cells 

 occupying the squares are counted, which can readily be 

 done, and the mean of them taken. 



In the horse the mean number of red blood corpuscles 

 per cubic millimetre* is 7,212,500, and in the ox 5,073,000. 

 Taking the amount of blood in the horse at 66 lbs., this 

 gives 204,113,750,000,000 as the approximate number of 

 red cells in the body (Ellenberger).t They are increased 

 by sweating, the excretion of water by the bowels and 

 kidneys, and by starvation ; they are diminished by 

 pregnancy and copious draughts of water (Landois and 

 Stirling). 



Each red cell offers a certain absorbing surface for oxygen, 

 which, if calculated on the total number of corpuscles, is 

 something enormous, being equal for the horse to a square 

 having a side of 140 yards. 



By freezing and thawing the blood alternately, also by 

 the addition of certain reagents to it such as chloroform, 

 ether, bile salts, etc., the red blood cells can be so broken up 

 as to liberate the colouring matter or haemoglobin, which 

 then deeply stains the serum, which is naturally yellow or 

 colourless. The broken-up red cells do not now reflect 

 light, and when this occurs the serum is seen of a red or 

 laky colour and quite transparent ; this is termed laky 

 blood. Blood in its natural state, as previously mentioned, 

 is opaque, but when treated by the above methods, or by 

 electrical shocks, it becomes transparent. 



The greater part of the red cell is haemoglobin, a sub- 

 stance possessing a remarkable affinity for oxygen, which 



* A cube having its edges about one-twenty-fifth of au inch. 

 •f ' Physiologie der Haussiiugethiere.' 



