Neutral Stains 247 



made up with more certainty of obtaining a satisfactory product. 

 Ordinarily today, however, one purchases his blood stains already 

 prepared by some manufacturer; and the Wright stain on the 

 market seems to be as reliable as the tetrachrome stain. 



Giemsa stain, although originally intended to be more definite 

 in composition than other blood stains, is possibly the most com- 

 plicated of them all. As a simple stain for blood in thin smears, 

 some find it to have no distinct advantage over stains of the 

 Leishman-Wright type, although others claim it to show greater 

 purity of color and sharpness of definition, with deeper staining of 

 chromatin; such advantages as it has for this purpose are offset 

 by the longer staining time and larger volume of solutions required. 

 As a stain for malarial blood, however, designed to show the 

 malaria plasmodium, Giemsa stain is definitely preferred. In 

 searching for the malaria organism the present approved technic 

 calls for the use of thick smears of blood in which laking of the red 

 corpuscles is brought about by distilled water (either as a diluent 

 of the stain or placed on the smears before staining) ; accordingly a 

 stain for the red cells* is not required, but one is necessary that 

 brings out the leucocytes and the plasmodia. For this, a prop- 

 erly prepared Giemsa stain has decided advantages over Wright 

 stain. Good results have quite consistently been obtained with 

 the German Giemsa stain, when it has not become unavailable 

 because of war; and there is good reason to believe that it has been 

 quite constant in composition. As remarked above, its manufac- 

 turers used to lay considerable stress on the /'secret" character 

 of azure I and to claim that since they alone know that secret, no 

 other Giemsa stain except theirs could be reliable. As mentioned 

 above, however, no real secret seems to have been involved; and 

 recent investigations have shown that a Giemsa stain, having one 

 of its absorption maxima at about 655, as recommended by Lillie 

 (whether prepared in the laboratory or put on the market as a 

 commercial product) is an excellent malarial stain, as judged by 

 technicians familiar with the technic in question. 



During the two decades from 1920 to 1940, however, much 

 Giemsa stain was on the market in America which did not conform 

 to the requirements now specified by Lillie. This was largely due 

 to the stress laid by MacNeal on Azure A as the important in- 

 gredient of azure I, and to the fact that Holmes and French later 

 (1926) said quite definitely that azure B has no staining value. It 

 took some time to counteract the effect of such statements, and 

 meanwhile American manufacturers of Giemsa stain, with the 

 endorsement of the Stain Commission, used azure A, without any 

 appreciable azure B, in its preparation. Since Lillie has called 

 attention to the importance of azure B, however, the practice of 

 the stain companies has changed; and now there is an American 



