BLOOD AND LYMPH. l8/ 



have an entirely different origin in the liver namely, from the large 

 polynuclear, giant cells, which are thought to arise either from the 

 cells of the capillaries or from the liver-cells (Kuborn, M. Schmidt). 



Late in fetal life and in the adult, the red bone-marrow and the 

 spleen are the organs which form the red blood-cells. The lym- 

 phatic glands and the spleen produce the white blood-cells. In ad- 

 dition to the nucleated red corpuscles which are present up to a cer- 

 tain stage of development, nonnucleated red blood-cells also appear. 

 The number of the latter increases, until finally they are found 

 almost exclusively in the blood of the new-born infant. 



The blood of the adult consists of a fluid, coagulable substance, 

 the blood plasma, and of formed elements suspended in this inter- 

 cellular substance. The fluid medium of the blood is of a clear 

 yellowish color and of alkaline reaction, having a specific gravity 

 of about 1030. It is made up of water, of which it contains about 

 90 % , and various organic and inorganic substances. The formed 

 elements are : (a) Red blood-corpuscles (erythrocytes) ; (b) white 

 blood-corpuscles (leucocytes); and (r) the blood platelets of Biz- 

 zozero (82), hematoblasts of Hayem, or the thrombocytes of 

 Dekhuysen. Besides. these, there are present particles of fat, and, 

 as H. F. Miiller (96) has recently shown, also hemokonia. 



2. RED BLOOD-CORPUSCLES. 



In man and nearly all mammalia the great majority of the red 

 blood-corpuscles are nonnucleated, biconcave circular discs with 

 rounded edges. They have smooth surfaces, are transparent, pale 

 yellowish-red in color, and very elastic. No method has as yet 

 been devised to demonstrate a nucleus in these cells, and there is no 

 doubt that the red blood-discs of the human adult and of mammalia 

 are devoid, in the histologic sense, of a nucleus capable of differen- 

 tiation (compare Lavdowsky ; Arnold, 96). They are therefore 

 peculiarly modified cells. They possess a somewhat more resistant 

 external zone of exoplasm, which has been interpreted as a cell 

 membrane by certain observers (Lavdowsky), but which does 

 not present the characteristics of a true cell membrane. 



If fresh blood be left for some time undisturbed, the blood-discs 

 adhere to each other by their flattened surfaces, grouping them- 

 . selves in rouleaux. 



By certain reagents the clear and transparent contents of the 

 blood-corpuscles can be separated into two substances a staining 

 and a nonstaining. The first consists of the blood pigment, or 

 hemoglobin, which can be dissolved ; the second of a colorless sub- 

 stance, the stroma, which presents itself in various forms (protoplasm 

 of the cell). The stroma probably contains the hemoglobin in solution. 



Hemoglobin is a very complex proteid which may be decom- 

 posed into a globulin and a pigment hematin. The hemoglobin of 

 the majority of animals crystallizes in the form of rhombic prisms ; 



