210 MICROMETRY AND BLOOD PREPARATIONS 



glasses which are to be used for blood-work. This is the best method 

 of getting rid of grease. 



Thick Film Methods. Such methods are of the greatest practical 

 value in diagnosis of malarial parasites when in very small numbers 

 in the peripheral circulation. They are also of great value in finding 

 trypanosomes, relapsing fever spirochaetes and filarial embryos in the 

 blood. Ruge's method so brings out the polymorphonuclears that 

 such a technic can be used for opsonic index. 



Method of Ross. In this about one-half of a drop of blood is smeared out over a 

 surface about equal to that of a square cover-glass and allowed to dry. It is then 

 flooded with a 0.1% aqueous solution of eosin for about fifteen minutes. The prepa- 

 ration is then gently washed with water and then treated with a polychrome 

 methylene-blue solution. After a few seconds this is carefully washed off and the 

 preparation dried and examined. 



Method of James. -James smears out an ordinary drop of blood so that it makes a 

 circular smear about % inch in diameter. This may be easily accomplished with a 

 spatulate wooden toothpick. When dry, treat the blood smear with alcohol contain- 

 ing HC1. (Alcohol 50 c.c. HC1. 10 drops) until the haemoglobin is dissolved out. 

 Then wash thoroughly in water for five or ten minutes. Allow to dry and then 

 stain as ordinarily with the Wright or Giemsa stain. 



Ruge's Method. The best thick film method is that of Ruge. After the blood 

 has dried well, gently move the slide about in a glass containing a 2% solution of 

 formalin to which has been added i% of glacial acetic acid. After laking is com- 

 plete, as shown by disappearance of brown color, treat the slide in the same way in a 

 glass of tap water to remove all traces of acid. Next wash very gently in distilled 

 water and stain with dilute Giemsa (i drop to i c.c.) for twenty to thirty minutes. 

 Wash in water and allow to dry without heat or blotting paper. 



Some workers prefer to stain the dried thick smear for one hour in a jar containing 

 dilute Giemsa stain (i to 40) without previous fixation or dehaemoglobinization. 



At present, I make my thick films by taking up a moderately large 

 loopful from the exuding drop of the puncture wound. 



This is deposited at one end of the slide and from it three or four more 

 daubs are made in succession toward the other end of the slide. 

 These daubs are quickly smeared out before coagulation takes place 

 in the first daub. 



With all thick film methods it is extremely important to have thorough drying 

 of the smear before dehaemoglobinizing or staining. This ordinarily requires one or 

 two hours in the air or twenty to thirty minutes in the incubator. It is particularly 

 important in working with such smears, although holding for ordinary smears, to 

 protect them from flies, ants, etc., as such insects will eat up the smear in a few 

 minutes if left exposed. 



Fixation of Film. In Wright's, Leishman's, and other similar stains the methyl- 

 alcohol solvent causes the fixation. In staining with Giemsa's stain, Ehrlich's 



