Since the bacillus of Pfeiffer commonly occurs in association with other organisms in the lungs and other tissues, it is difficult to make the organisms appear distinctly in stained sections. There are many methods by which they or any other gram-negative organisms can be stained in the tissues (Nicolle, Giemsa, etc.), but these require very careful differentiation and then leave all bacteria, whether gram-negative or gram-positive, stained alike. One may, of course, stain all bacteria in one section and only the gram-positive organisms in another, and subtract the result in one from that in the other, so as to gain an idea of the number and distribution of gram-negative organisms; but it is very desirable to be able to bring out in the same section the gram-negative bacteria in one color and the gram-positive in another.
The stain devised by Dr. Goodpasture furnishes the requisite red stain for all bacteria.