THE BLOOD-PLATELETS S7 



from the plasma, which Wooldridge recognised, or the bodies 

 described by J. Arnold ! as artificially produced when blood is 

 treated with 10 per cent, potassium iodide. The only possible 

 evidence which can be adduced for the decision of this question, 

 which we admit is of cardinal importance, is the aspect of the 

 so-called true and false platelets, together with their behaviour 

 to various stains. We believe that it is difficult, if not impossible, 

 to make this distinction, and consider that since the platelets 

 can be seen to actually form under the microscope in numbers 

 sufficient to give a count of about 500,000 per c.mm., they arise 

 from admixture of the fixing fluids with the blood-plasma. 

 Human plasma cannot be collected free from platelets, for either 

 the lowering of temperature or the substance which is added to 

 prevent coagulation induces damage and consequent alterations 

 in the fluid, and our own observations lead to the belief that 

 plasma alters more rapidly outside the body than any living cell 

 of the organism. 



In 1897 H. Deetjen 2 described a new method for the study of 

 blood-platelets. When human blood comes in contact with a 

 sheet of agar which contains 7 per cent, of NaCl, the prepara- 

 tion shows innumerable amoeboid platelets either separate or in 

 groups of ten to twenty. In 1901 he published the composition 

 of another medium, which consisted of: 



Agar-agar 1-2 grammes. 



Distilled water 100 c.c. 



NaCl 6 grammes. 



This is filtered, and 7 c.c. of a 10 per cent, solution of sodium 

 metaphosphate and 5 c.c. of a 10 per cent, solution of potassium 

 phosphate are added. The mixture must not be boiled after the 

 addition of these solutions. 3 



A drop of blood is allowed to spread out on a thin sheet 

 of the medium, and the preparation is covered. Under the 

 microscope large numbers of nucleated flattened platelets, each 

 of which may possess several fine processes, can be immediately 

 seen ; many of the bodies adhere to the cover-glass, and, in 

 Deetjen's words, convey the impression of a miniature starry 



1 " Zur Morphologie und Biologie der voten Blutkorperchen," Virch. Archiv, 

 cxlv. 1896. 



2 " Eine Methode zur Fixirung der Bewegungszuslande von Leukocyten und 

 Blutplattchen," Munch med. IVochenschrift, s. 1192, 1897. 



3 " Untersuchungen iiber die Blutplattchen," Virch. Archiv, clxiv. 1901. 



