372 R. W. GLASER AND J. W. CHAPMAN. 



matter of fact, a smear made from a recently wilted caterpillar 

 is almost devoid of bacteria, and in many cases none at all can 

 be found. If bacteria are present, they have escaped into the 

 body cavity through rupture of the intestine and bear no direct 

 etiological relation to the disease. 



In fixed and stained smears a number of things can be demon- 

 strated to advantage within the polyhedra. Fixation was accom- 

 plished either by passing the preparation through a flame or by 

 placing it in absolute alcohol for a few minutes. The smears 

 were then stained in Giemsa's solution for 12 hours or were stained 

 for a shorter period with one of the following dyes: Methylene 

 blue, trypan blue, gentian violet, carbol fuchsin, Bismarck brown, 

 or iron haematoxylin. When iron hsematoxylin was used, the 

 preparation was first mordanted in a 4 per cent, ferric-alum 

 solution for two or three hours. After staining, the preparations 

 were sometimes quickly passed through the alcohols to xylol 

 before mounting. This not only clears everything, but dissolves 

 away all the fat on the slide and thus increases the transparency 

 of the preparation. Gipsy moth polyhedra are rather resistant 

 to stains in general and usually color along the periphery only, 

 unless the stain is applied for a long time. When this is done 

 one may succeed in staining the entire polyhedron, /especially 

 after the use of some mordant like ferric alum before hematoxylin 

 or anilin water before gentian violet. Steaming the preparation 

 with a stain like carbol fuchsin has also given good results. 

 When properly stained, one of three conditions is observed: 

 First, the polyhedral bodies are uniformly stained so that nothing 

 can be detected within them; or second, a uniformly darker 

 staining central mass can easily be differentiated from an almost 

 unstained outer substance; or, third, many little refractive, 

 reddish granules are seen within the polyhedra. An actual 

 differentiation between what might be interpreted as nuclear 

 and cytoplasmic material within the polyhedra never occurs. 

 Therefore, in accounting for the staining reactions we believe 

 that at times the polyhedra have a central granular or homo- 

 geneous substance easily distinguishable from an outer tougher 

 substance which is more resistant to the dyes. This varies a 

 great deal, however, and sometimes the periphery takes the 



