CH. XXIX.] CHEMISTRY OF BLOOD-CORPUSCLES 461 



Origin of the White Corpuscles. The lymphocytes are formed 

 in the lymphoid tissue of the lymphatic glands, tonsils, and other 

 parts where this tissue is present. They enter the blood-stream by 

 the thoracic duct, and grow larger, the proportion of protoplasm to 

 nucleus increasing as they become mature. The mononuclear leuco- 

 cyte is, according to some, a mature lymphocyte ; some think it 

 is endothelial in origin (see p. 456); according to others, it, like the 

 polynuclear leucocytes, originates from immature forms in the red 

 marrow, which are called myelocytes. The leucocytes proper, as 

 distinguished from the lymphocytes, do not grow larger in the blood- 

 stream, but rather have a tendency to shrink in size with age. 



If immature myelocytes escape from the marrow into the circu- 

 lating blood, they undergo no further development there, and like 

 the immature nucleated red corpuscles, are filtered off by the spleen. 

 This, of course, is a pathological condition, and leads to the swelling 

 of the spleen, which is such a marked feature in the disease known 

 as splenic leukaemia. 



Chemistry of the Blood- Corpuscles. 



The white blood-corpuscles. Their nucleus consists of nuclein, 

 their cell protoplasm yields proteins belonging to the globulin and 

 nucleo-protein groups. The protoplasm of these cells often contains 

 small quantities of fat and glycogen. 



The red blood-corpuscles. 1000 parts of red corpuscles con- 

 tain 



Water . 688 parts. 



Solids /Organic 303-88 



ls \Inorganic 8'12 



One hundred parts of the dry organic matter contain 



Protein 5 to 12 parts. 



Haemoglobin 86 to 94 



Phosphatides calculated as lecithin . . . . 1 '8 



Cholesterin O'l 



The protein present appears to be identical with the nucleo-protein 

 of white corpuscles. The mineral matter consists chiefly of chlorides 

 of potassium and sodium, and phosphates of calcium and magnesium. 

 In man potassium chloride is more abundant than sodium chloride ; 

 this, however, does not hold good for all animals. 



Haemoglobin and Oxy haemoglobin. The pigment is by far 

 the most abundant and important of the constituents of the red 

 corpuscles. It is a conjugated protein, a compound of protein with 

 the iron-containing pigment called haematin. 



It exists in the blood in two conditions : in arterial blood it is 

 combined loosely with oxygen, is of a bright red colour, and is called 



