432 HEALTH AND DISEASE 



by numerous observers, and three chief forms of corpuscles have been 

 distinguished, named, respectively, red corpuscles, white corpuscles, and 

 blood platelets. 



The red corpuscles are pale-yellow circular discs, each resembling a coin, 

 with edges thicker than the central part, and they are hence said to be 

 biconcave. Their consistence is like that of moderately firm jelly. They 

 have no nucleus. The transverse diameter is about -g-^oo inch, and their 

 thickness about ttooo inch. They are a little heavier than the fluid in 

 which they are suspended, and consequently have a tendency to fall to 

 the bottom of the vessel when blood is removed from the body. This 

 disposition to gravitate may be observed in the living animal, since if 

 blood be gently drawn with a small syringe from the upper and lower 

 parts of a large horizontal vein — like the external jugular or neck rein 

 when the animal is recumbent — the number of the corpuscles contained 

 in the specimen taken from the lower part of the vein will be found to 

 be much greater than in the specimen taken from the upper part. The 

 number of the corpuscles in the body of a horse is inconceivably great, 

 but they may be counted in small quantities of blood which have been 

 diluted with water, and it has been ascertained that there are no less 

 than five or six millions in a cube -^ inch on the side, which would be 

 represented by a very small drop. In every hundred parts of the red 

 corpuscles there are about seventy parts of water and thirty parts of solids, 

 and if the solids be examined after the water has been evaporated, every 

 hundred parts are found to consist of eighty-eight parts of haemoglobin, 

 ten parts of proteid substance of the nature of globulin, and two parts of 

 lecithin and cholesterin. The haemoglobin then is the most abundant, as 

 it is the most important, constituent of the blood. It is to it that the blood 

 owes its colour, and it possesses L3veral remarkable properties. In the first 

 place, it is one of the prime factors in the process of respiration, being the 

 carrier of oxygen between the air and the tissues, combining with this gas 

 in the lungs, but holding it with so weak a grasp as to surrender it to the 

 tissues during the brief period that it is in proximity with them whilst 

 traversing the more minute or capillary vessels. It is possible, although it 

 has not as yet been proved, that haemoglobin presents similar relations 

 with carbon dioxide, taking up that gas in the tissues, in exchange for the 

 oxygen with which it parts, and permitting its escape at the lungs in 

 exchange for the oxygen it there absorbs. In this case it would serve as a 

 carrier for both oxygen and carbon dioxide, its relations to each gas being 

 governed by the degree of chemical affinity between the haemoglobin and 

 the gas and by the tension of the gas at the moment of exposure to it. 

 Experiment has shown that every ten grains of haemoglobin is able to 



