THE BLOOD. 147 



corpuscles will be observed slowly to alter their shapes, and to send out 

 processes at various parts of their circumference. The amoeboid move- 

 ment which can be demonstrated in human colorless blood-corpuscles, 

 can be most conveniently studied in the newt's blood. The processes 



Fig. 128. Human colorless blood-corpuscles, showing its successive changes of outline withtf 

 ten minutes when kept moist on a warm stage. CSchofield.) 



which are sent out from the corpuscle are either lengthened or with- 

 drawn. If lengthened, the protoplasm of the whole corpuscle flows as 

 it were into its process, and the corpuscle changes its position; if with- 

 drawn, protrusion of another process at a different point of the circum- 

 ference speedily follows. The change of position of the corpuscle can 

 also take place by a flowing movement of the whole mass, and in this 

 case the locomotion is comparatively rapid. The activity both in the 

 processes of change of shape and also of change in position is much 

 more marked in some corpuscles than in others. Klein states that in 

 the newt's blood the changes are especially noticeable in a variety of the 

 colorless corpuscle, which consists of a mass of finely granular proto- 

 plasm with jagged outline, and contains three or four nuclei, or in large 

 irregular masses of protoplasm containing from five to twenty nuclei. 



Action of reagents upon the colorless corpuscles. Feeding the corpus- 

 cles. If some fine pigment granules, e.g., powdered vermilion, be added to a 

 fluid containing colorless blood-corpuscles, on a glass slide, these will be 

 observed, under the microscope, to take up the pigment. In some cases 

 colorless corpuscles have been seen with fragments of colored ones thus em- 

 bedded in their substance. They have also been seen, in diseased states, to 

 contain micro-organisms, e.g., bacilli, and according to some pathologists are 

 capable of destroying them (phagocytosis) . They may too take up other for- 

 eign matter or even other colorless corpuscles. This property of the colorless 

 corpuscles is especially interesting as helping still further to connect them with 

 the lowest forms of animal life, and to connect both with the organized cells of 

 which the higher animals are composed. 



The property which the colorless corpuscles possess of passing 

 through the walls of the blood-vessels will be described later on. 



The Blood-Plates. A third variety of corpuscle is found in the 

 blood, and is known as the Hood-plate. It is circular or elliptical in 

 shape, of nearly homogeneous structure, and varies in size from .5-5.5;*. 

 Hence it is smaller than the red cell. Though found in the circulating 

 blood, they are not independent cells. It is altogether probable that they 

 are derived chiefly from the red cells, being extruded therefrom in the 



