THE BLOOD. 257 



Origin of White Corpuscles. The white corpuscles which are 

 present in the blood are believed to be derived from the lymphocytes 

 or lymph- corpuscles which find their way into the bloocfat te points 



wEere the lymph-ducts discharge their lymph: viz., at the iynr- 



the cours 



fagylar and siifrla.vifl.fl wins. Along the course 

 of~trie~lymph- vessels are to be" found, in different regions of the 

 body, numerous lymph-glands the meshes of which are filled with 

 small, colorless, nucleated cells, which arise by self-division and rep- 

 resent the early stages in the development of lymphocytes. Similar 

 corpuscles are found in the mucous membranes, skin, spleen, and the 

 fluids of the tissues. As the lymph flows through the glands these cells 

 are washed out and carried direct to the blood. In their passage they 

 grow in size by increasing the amount of their cytoplasm and even- 

 tually become normal adult leukocytes. After an unknown period 

 of life they undergo dissolution and disappear. 



Chemic Composition. The chemic composition of the white 

 corpuscles has been inferred from an analysis of pus-corpuscles, 

 with which they are practically indentical, and of lymph-corpuscles 

 from the lymph-glands. Of the corpuscle about 90 per cent, is 

 water and the remainder solid matter consisting mainly of proteids, 

 of which nuclein, nucleo-albumin, and cell globulin are the most 

 abundant. The two former are characterized by the presence of a 

 considerable quantity of phosphorus, amounting to as much as 10 

 per cent. Lecithin, fat, glycogen, and earthy and alkaline phos- 

 phates are also present. 



Functions. The functions of the white corpuscles are but im- 

 perfectly known, and at present no positive statements can be made. 

 It has been suggested that wherever found in the body, whether in 

 blood or tissues, they are engaged in the removal of more or less in- 

 soluble particles of disintegrated tissues, in attacking and destroying 

 more or less effectively various forms of invading bacteria and thus 

 protecting the body against their deleterious activity. This they do 

 by surrounding, enveloping, and incorporating either the tissue par- 

 ticle or bacterium and digesting it. On account of this swallowing 

 action these cells were termed by Metchnikoff phagocytes and the 

 process phagocytosis. He regards them as the yen era] ggayenffiers-pf 

 the body. It has been suggested that they are also engaged in 

 the absorrjlion^offat from the lymphoid tissue of the intestine. In 

 their dissolution TliUy lUMabule Lu trie blood-plasma ceriain^oteid 

 materials which assist under favorable circumstances in the coagu- 

 lation of the blood. 



HISTOLOGY OF THE BLOOD-PLATES. 



The blood-plates or plaques are small histologic elements circu- 

 lating in the blood-plasma. They were discovered by Hayem, who 



