SECTION III 

 THE BLOOD-PLATELETS 



THE very existence of these, the third class of formed elements of 

 the blood, is still a matter of dispute. If a drop of osmic acid be placed 

 on the finger, which is then pricked through the drop so that the shed 

 blood may mix with the fixing fluid directly it leaves the vessels, a 

 drop of the mixture when examined under high powers is seen to 

 present a number of granular bodies from one-third to one-half the 

 diameter of a red blood-corpuscle. Their number has been variously 

 stated from 180,000 to 800,000 per cubic millimetre, so that they 

 rank second in point of number among the morphological constituents 

 of the blood. Their shape varies considerably. Some are bi-convex 



FIG. 363. Blood-platelets, highly magnified, showing the amoeboid 

 forms which they assume when examined under suitable con- 

 ditions, and also exhibiting the chromatic particle which each 

 platelet contains, and which has been regarded as a nucleus. 

 (After KOPSCH.) 



structures ; others are flatter with numerous processes. They may be 

 isolated or agglutinated into clumps. Their shape, size, and number 

 vary according to the fluid with which the blood is mixed or the method 

 adopted for their demonstration. When blood is examined in 

 Hayem's fluid * nearly all the blood-platelets appear as bi-convex discs. 

 The best method for the display of platelets is apparently that given 



* Hayem's fluid is made up as follows : 



Distilled water 200 c.c. 



Sodium chloride ...... 1 grm. 



Sodium sulphate ...... 5 grm. 



Iodine in iodide of potassium .... 3-5 c.c. 



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