BLOOD PLATELETS 



47 



BLOOD SMEARS 



TABLE 2 



Characteristics of various indirect methods of platelet 

 enumeration 



« Arch. Path., 1937, 23, 850. 



*J. A. M. A., 1923,80,621. 



' J. A. M. A., 1905, 45, 1999. 



''Arch. Int. Med., 1932, 50, 579. 



• Deutsche Ztschr. f. Chir., 1912, 117, 176. 



/J. A. M. A., 1921,76,427. 



ePrit. Med. J., 1901,2, 1539. 



''Lancet, 1929, 1,992. 



depending upon the methods employed. 

 The range of reported normal platelet 

 counts in man has varied from a mini- 

 mum of 130,000 per cu. mm. (2) to a 



maximum of 900,000 per cu. mm. (3) 

 Since all methods so far devised are 

 subject to inherent errors, there is no 

 sound basis for a choice between the 

 mutually exclusive standards of normal- 

 ity which have been reported.* 



Blood Protein. Coagulated blood protein 

 within the vascular lumina of stained 

 sections of fixed tissues is an artifact 

 in the sense that its appearance has been 

 greatly modified by the technique. It 

 is sometimes made up of particles of 

 quite uniform size and has been 

 mistaken for masses of microorganisms ; 

 but it docs not exhibit both acidophilic 

 and basophilic staining reactions sug- 

 gestive of cytoplasmic and nuclear 

 components. 



Blood Smears. These should be made on 

 slides rather than on cover glasses for 

 several reasons. A larger film of blood 

 is thereby provided for examination. 

 Smears on slides are easier to make and 

 to handle. They can be studied without 

 covering them whereas a smear on a 

 cover glass cannot be moved about on 

 the stage of the microscope unless it is 

 mounted smear side down on a slide. 

 The colors are often more permanent in 

 smears on slides which are not covered 

 with cover glasses. A good way is to 

 spread a thin film of immersion oil over 

 them. This dries much more quickly 

 than balsam or any other medium under 

 a cover glass. 



Slides of good quality with ground 

 edges and scrupulously clean are neces- 

 sary (Cleaning Glassware). A finger 

 tip or ear lobule is first cleaned with 95% 

 alcohol. As soon as the surface^ has 

 dried a small puncture is made with a 

 previously sterilized needle. Special 

 needles with lance shaped cutting ends 

 are better than ordinary pointed ones. 

 A small droplet of blood should appear 

 on slight pressure. The first is wiped 

 away with sterile gauze and the second 

 and following ones are used. Unless 

 the blood is very strongly pressed out, 

 the differential count of white cells will 

 not be affected. Some advise holding 

 the fingers in hot water beforehand to 

 produce a temporary hyperemia in them 

 but this is seldom advisable. A droplet 

 of size sufficient to produce a smear of 

 the desired thickness (determined by 

 trials ) should be touched to the surface of 

 a slide about 3 cm. from one end conven- 

 iently placed on a table. Immediately 

 the end of a second slide, with its edge 



• Original observations and confirmation of published 

 data contained in tliis paragraph were done under a con- 

 tract (No. AT-ll-l-GEN-10, Project 2), between the 

 United States Atomic Energy Commission and the Uni- 

 versity of California. 



