124 DIFFUSION- VACUOLES 



is clear that the blood-platelet is a living cell and 

 not a precipitate. As far as we know, no precipitate 

 has a coefficient of diffusion, and even if such a 

 thing were possible, one certainly could not lower it 

 by causing approaching death with morphia. 



Blood-platelets unquestionably are living cells; and 

 they can actually be seen to be produced by leuco- 

 cytes when they are examined on a jelly-film by 

 this method. They are all the same class of cell, ap- 

 parently produced in the same manner. If a speci- 

 men of fresh blood is spread on a jelly which contains 

 stain and an alkaloid such as atropine sulphate, as 

 will be described in the next chapter, the leucocytes 

 and the lymphocytes become excited and extrude long 

 pseudopodia. Sometimes these pseudopodia become 

 detached from the cells (fig. 26), when the fragment 

 appears to be identical with a blood-platelet. They 

 may contain a few granules derived from the leucocytes. 

 Moreover, the blood-platelet is also highly amoeboid 

 under this excitation; and their amoeboid movements 

 can easily be seen by this method. Deetjen, several 

 years ago, asserted that blood-platelets showed amoeboid 

 movements, although, of course, he did not employ 

 alkaloids to excite them. By this method, however, 

 not only can they be readily seen to show movements, 

 but they have also actually been photographed in the 

 act (fig. 27). We have also succeeded in obtaining 

 a negative of a blood-platelet apparently being produced 

 by a leucocyte (fig. 26) . As a matter of fact, the plate- 

 lets stained by this method have such a remarkable 

 resemblance to leucocytes that in the very earliest 



