MAMMALIA— PHYSIOLOGY 457 



Red corpuscles or erythrocytes consist of water, hemoglobin, 

 nucleoproteid, lecithin, cholesterin and salts of potassium and of 

 phosphoric acid. The erythrocytes of fishes, amphibia, reptiles and 

 birds are oval and nucleated and the leucocytes are frequently 

 found to be without nuclei. The erythrocytes are biconcave discs 

 in all mammals except the Camelidae in which they are oval^ but in 

 healthy animals, non-nucleated in adults as in other mammals.^ 

 Sometimes in man after anemia or severe hemorrhage, nucleated 

 reds are called forth from the red bone marrow where they are 

 formed in adults. In the embryo, the liver and the spleen produce 

 nucleated reds, but in the adult the spleen devours worn out reds 

 and furnishes some lymphocytes. The spleen probably takes some 

 of the iron from worn out red blood corpuscles while the liver takes 

 iron and uses hemoglobin in forming bile-pigment, bilirubin. The 

 thymus, tonsils and other lymphoid glands supply leucocytes, 

 acting as foci of multiplication for the cells which originate as 

 myelocytes in the bone marrow. 



When blood is treated with Os04 it shows colorless, round disks, 

 which are unstable, and also granules. The disks are " thrombo- 

 plastids" or blood platelets.'^ The proportion of red corpuscles to 

 platelets is as 80 : i or as 20 : i. They are foci where coagulation 

 of the blood is hastened. F. F. Lucas has photographed blood 

 platelets with ultra-violet light and discovered that they have 

 ." naked, sticky surfaces " such that they are able to glue themselves 

 together with available blood corpuscles and facilitate rapid blood 

 clotting. Howell believes that platelets are more than mechanical 

 agents in causing coagulation of blood and lymph. 



Blood Groups. — In blood transfusions, it is necessary that the 

 blood of the donor and the recipient be alike, and that the substance 

 known as a hemolysin be absent. In hemolysis, a substance is 

 produced which has the power of dissolving the introduced red 

 corpuscles. Hemolysis does not occur without agglutination 

 (clumping) (see page 458) and it is therefore only necessary to test 



* Since two texts of recent date have published the erroneous statement that Cam- 

 elidae have nucleated erythrocytes, the question was referred to Dr. W. H. F. Addison 

 and to Dr. Noback, both of whom reported that they are oval, biconvex and non- 

 nucleated. A paper by Ponder, Yeager and Charipper, Haematology of the Camelidae, 

 Zoologica, vol. ii, no. i, Dec. 5, 1928, furnishes additional proof. 



* Corson, Irwin and Phillips found (1930) that irradiated ergosterol (Vitamin D) 

 increased the number of thrombocytes in the blood of rats, and materially shortened 

 the time of coagulation. Blood calcium was increased. 



