EXAMPLE 17 



Demonstration of Diplococci in the Liver of the 



Rabbit, Using the Phloxine-M ethylene Blue-Azur 



II Stain of Mallory, 1938 



This method of Mallory is the best of all the eosin-methylene blue 

 methods that have from time to time been suggested for staining bacteria 

 in sections. It has the advantage of giving a first-class histological stain, 

 in addition to differentiating bacteria, and it might well be used as a 

 standard procedure in place of the more customary hematoxylin-eosin, at 

 least in pathological investigations. The liver of a rabbit is so frequently 

 infected with diplococci that it has been selected as a type demonstration, 

 for such infected animals will be found in ordinary laboratory investiga- 

 tions, making it unnecessary to go to the trouble of infecting a rabbit 

 for the purpose of obtaining the necessary demonstration material. 



If, then, in the course of routine dissections, a sacrificed rabbit is 

 found to have a pneumococcal infection of the liver, which may easily 

 be seen as yellow lesions on the surface, it is only necessary to cut the 

 lesion and some surrounding tissue and to place it in a suitable fixative. 

 Mallory himself recommends fixation in Zenker for about 24 hr. As Zenker 

 contains mercuric chloride, it is undesirable that the specimen should 

 remain in it for more than 3 or 4 days, but the actual time of fixation is not 

 critical. As always, when dealing with dichromate fixatives, a large quan- 

 tity of fixative should be used, and the object should be suspended in 

 the fixative solution in a loose cloth bag. When fixation is complete, the 

 pieces are removed from the fixative and washed in running water over- 

 night. They are then embedded in paraffin and sectioned in the ordinary 

 manner. Sections of from 5 to 8 /x are desirable if it is intended to 

 demonstrate the bacteria, although these are readily seen in the 10-^ 

 sections customarily employed for histological examinations. When the 

 sections have been fixed on the slide, they may, if desired, be freed from 

 the last traces of mercuric chloride by treating them with iodine and 



238 



