266 James Homer Wright. 



In sections of the blood forming organs, and of blood vessels 

 containing blood, stained by this special method, the blood plate- 

 lets present the following appearances and characteristics. They 

 consist of a hyaline blue staining substance in which are imbedded 

 closely set, minute, red to purple staining granules. In deeply 

 stained preparations this hyaline ground substance may not be 

 apparent. Their well known disc shape is sometimes preserved 

 so that they may appear as short rod-like bodies when viewed in 

 certain positions. Their margins may be smooth or show irregular, 

 small projections, of the hyaline ground substance. Elongated 

 forms, sometimes several times as long as broad, occasionally 

 occur. These have been described by F. Weidenreich in smear 

 preparations. The red to purple staining granules may be aggre- 

 gated in a more or less sharply outlined mass in the central part 

 of the platelet so as to suggest a nucleus surrounded by a hyaline 

 cytoplasm. In some platelets a clear, unstained, more or less 

 sharply outlined vacuole-like area may be seen in the midst of 

 the granules. This has also been noted in smear preparations by 

 G. Schmauch and by F. Weidenreich. 



The structure of the blood platelets, and especially the peculiar 

 color taken l?y the granules within them, are very characteristic 

 and sharply distinguish them from the other elements of the blood. 

 The red corpuscles and granular precipitates caused by certain 

 fixing agents in the plasma stain pink or green depending on the 

 fixative used and the intensity of the staining. The nuclei of the 

 leukocytes stain blue and the various kinds of granules in the cyto- 

 plasm of the leukocytes, according to the species of the animal, 

 may or may not be characteristically stained as in smear prepara- 

 tions stained by modern blood staining methods. 



Blood platelets, with the staining and other appearances above 

 described, are found in sections of vessels doubly ligated during 

 life in numbers corresponding to the numbers of the blood plate- 

 lets in fresh blood. Moreover, in sections of material properly 

 fixed by formaldehyde, in which no granular precipitate is produced, 

 all bodies which are of the shape and size of blood platelets stain 

 characteristically. For these reasons it is believed that all of 



