THE CIRCULATORY SYSTEM. IIX 



These bodies may be recognized in the circulating blood, as ob- 

 served by Osier and others, and are constant, although numerically 

 variable, elements of mammalian bloods. The peculiar elongated 

 elliptical ' ' blood-spindles' ' found in the blood of other vertebrates 

 are probably to be regarded as the homologues of the blood-plaques 

 of mammals. While the presence of the blood-platelets as distinct, 

 constant, and normal constituents of the human blood is now gener- 

 ally recognized, authorities are far from accord as to their significance. 

 The evidence at present seems to point to a close relation between 

 these bodies and the process of coagulation, in view of their probable 

 active role in the production of the factors in the formation of fibrin. 



Fibrin filaments are to be observed in a drop of blood mounted 

 in the usual manner for microscopical examination and allowed to 

 stand for some time in a moist chamber ; they appear as very delicate 

 straight interlacing threads which occupy the interspaces between 

 the corpuscles and frequently radiate from a common centre, con- 

 taining a group of partially broken-down blood-platelets. 



Additional minute particles are to be seen in human blood, 

 regarding the nature, source, and significance of which much has 

 been surmised and but little definitely established. These include 

 the small colored disks, the microcytes or the haematoblasts of 

 Hayem, according to whose authority they constitute an important 

 source of the red corpuscles ; by others they are regarded as sep- 

 arated portions of the ordinary red cells. Other minute, colorless, 

 often highly refracting, granules are encountered floating in the 

 liquor sanguinis ; such are the elementary particles of Zimmer- 

 mann and the granules of Max Schultze. These particles differ 

 in nature as well as in source ; some probably are derived from the 

 disintegration of the white corpuscles and of 

 the blood-platelets, others from that of the 

 endothelial plates of the vascular channels, 

 while many represent fatty granules absorbed 

 during digestion or taken up, possibly, in the 

 course of pathological processes. v * 



Blood-Crystals. The coloring matter of the Haemin cr y stals from dried 



i i i i "L i *- 1-1 11- human blood. 



blood the haemoglobin readily crystallizes 

 in man and most mammals as elongated, rhombic prisms ; the haemo- 

 globin crystals of the squirrel and of the guinea-pig, however, are 

 respectively hexagonal plates and rhombic tetrahedra. These blood- 

 crystals, of a deeper or lighter red color according to their size, often 

 form in preparations of blood which have been sealed and allowed to 

 stand after the addition of a few drops of water ; the blood of the 

 rat is especially favorable for their production. If dried blood be 

 treated and thoroughly mixed with glacial acetic acid (the addition 



