May IS. 191S Wilt of Gipsy- Moth Caterpillars 107 



polyhedra takes the stain more readily than the underlying strata. 

 From these staining reactions it becomes apparent that the polyhedra 

 of the gipsy moth are complicated in structure, thus not differing essen- 

 tially from what Bolle (i) and Prowazek (12, p. 277-281) found to be 

 true of the silkworm polyhedra. 



The polyhedra are heavier than water and consequently can be obtained 

 in bulk by centrifuging aqueous emulsions of diseased material. By 

 repeated washing and centrifuging, most of the fat, the cellular debris, 

 etc., can be eliminated and the polyhedra obtained in a fairly pure stage 

 for chemical tests. The writer has found, as did Prowazek (11) that i 

 per cent of sodium hydroxid or potassium hydroxid swells the polyhedra 

 to about double their normal size and that the same granular mass 

 observed above again becomes visible. After a time the granular mass 

 flows together and disappears, a sort of shadow remaining. On treating 

 the material with dilute hydrochloric or sulphuric acid, the granular 

 mass reappears and flows together ; then the periphery of the polyhedron 

 dissolves away, and a shadow remains, which also quickly vanishes. 

 The wilt polyhedra do not dissolve in hot or cold water, and are insoluble 

 in alcohol, ether, chloroform, xylol, and glycerin, but are soluble in strong 

 acids and alkalies. They do not blacken with osmic acid and do not 

 stain with Sudan III and therefore contain no fat. Picric acid stains 

 them yellow, showing that they are related to the albuminoid substances. 



So far nothing tangible has appeared that would enable the writer to 

 regard the polyhedral bodies as organisms, and therefore he believes them 

 to be reaction bodies belonging to the highly differentiated albumins — - 

 namely, the nucleoproteids. It will be shown later that the polyhedra 

 originate in the tissue nuclei; hence, the conception of nucleo- 

 proteid reaction bodies does not seem unjustifiable. Furthermore, ex- 

 periments discussed later in this article show that it is possible to infect 

 caterpillars with material from which the polyhedra have been removed. 



Although the writer has examined thousands of stained smears of 

 wilted caterpillars, he has never observed anything which could be asso- 

 ciated with the chlamydozoa as described in 1907 by Prowazek (11). 

 In his latest paper, however, Prowazek (12) himself says very little about 

 the chlamydozoa and therefore seems no longer to be greatly impressed 

 with their etiological importance. 



TECHNIQUE 



Before going into a detailed consideration of the pathology of the 

 tissues, a description of a number of the fixing and staining methods that 

 were used may not be out of place. 



The best results were obtained by the use of Giemsa's stain, Schaudinn's corro- 

 sive-sublimate fixation being used whenever this stain was employed. Hot water was 

 saturated with corrosive sublimate and allowed to cool. Two parts of this solution to 

 one part of absolute alcohol constituted the fixing fluid, which was used cold. The 



