THE BLOOD, 



157 



seen in all cases without the use of reagents. They are charac- 

 terized hy greater size, a globular form, the lack of pigment. 



s 



Fi«. 143. — Blood-plaques and their derivatives (Landois, after Bizzozero and Laker)*. 

 1, red blood-corpuscles on the flat; 2, from the side; 3, unchanged blood-plaques; 

 4, lymph-corpuscle surrounded with blood-plaques; 5, blood-plaques variously 

 altered; 6, lymph-corpuscle with two masses of fused blood-plaques and threads 

 of fibrin; 7, group of Dlood-plaques fused or run together; 8, similar small mass 

 of partially dissolved blood-plaques with fibrils of fibrin. 



and the tendency to amoeboid movements, which latter may be 

 exaggerated in disordered conditions of the blood, or when the 

 blood is withdrawn and observed under artificial conditions. 

 It will be understood that these cells (leucocytes) are not con- 

 fined to the blood, but abound in lymph and other fluids. 

 They are the representatives of the primitive cells of the em- 

 bryo, as is shown by their tendency (like ova) to throw out 

 processes, develop into higher forms, etc. In behavior they 

 strongly suggest Amoeba and kindred forms. 



We may, then, say that in all invertebrates the blood, when 

 it exists, consists of a plasma (liquor sanguinis), in which float 

 the cellular elements which are colorless ; and that in verte- 

 brates in addition there are colored cells which are always nu- 

 cleated at some period of their existence. The colorless cells 

 are globular masses of protoplasm, containing one or more 

 nuclei, and with the general character of amoeboid organisms. 



