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 os"mic 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 

 t r '^ number has been variously stated from 

 v F j| . , \ 180,000 to 800,000 per cubic millimetre, 



so that they rank second in point of 

 number among the morphological con- 

 stituents of the blood. Their shape 

 varies considerably. Some are bi-convex 

 structures ; others are flatter with 

 numerous processes. They may be iso- 

 lated 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 by Deetjen. The drop of blood is received directly from the vessels on to a sheet 

 of solid agar jelly which is made with 0-6 per cent, sodium chloride solution with the 

 addition of sodium metaphosphate and bipotassium phosphate. When examined on 

 this medium large numbers of platelets are seen, each of them provided with numerous 

 processes (Fig. 367). Their central part is more strongly refracting than the periphery 

 and stains with basic dyes, so that it has been regarded as a nucleus. 



Similar platelets are observed when the blood is received into normal 

 salt solution, and, as the mixture clots, the filaments of fibrin can be seen 



FIG. 367. Blood- platelets, highly mag- 

 nified, showing the amoeboid forms 

 which they assume when examined 

 under suitable conditions, and also 

 exhibiting the chromatic particle 

 which each platelet contains, and 

 which has been regarded as a nucleus. 

 (After KOPSCH.) 



* Hayem's fluid is made up as follows : 

 Distilled water 

 Sodium chloride 

 Sodium sulphate 

 Iodine in iodide of potassium 



836 



200 c.c. 

 1 grm. 

 5grm. 

 3-5 c.c. 



