NATURE OF POLYHEDRAL BODIES FOUND IN INSECTS. 379 



was next thought advisable to ascertain whether or not they are 

 nucleoproteins. It seemed likely that this would be the case 

 for the reason that they are formed in the nuclei of certain tissue 

 cells. Two grams of whole (unrubbed) polyhedra were digested 

 for one week in artificial gastric juice. After this time a micro- 

 scopic examination failed to reveal any polyhedra. Theoret- 

 ically, everything should have been decomposed excepting the 

 nucleins which have a high phosphorus content. At the end of 

 one week's digestion the material was filtered through and dried 

 on ash free filter paper. The paper containing the residue was 

 then cut into fine pieces and put into a platinum crucible with 

 an oxidizing mixture (Na 2 CO 3 (2 parts) + KNO 3 (i part)). 

 The material was slowly ignited and the residue dissolved in 

 weak HNO 3 . This solution was then warmed with the addition 

 of some NH 4 NO 3 in order to make the expected precipitate less 

 soluble. Lastly 5 per cent, molybdic acid was added. The 

 material was placed in an incubator and on standing a pronounced 

 yellow precipitate (ammonium-phospho molybdate) was formed. 



On the basis of this and the other tests described the polyhedra 

 meet all of the requirements of the nucleoproteins. Nucleo- 

 proteins give all the color reactions, are soluble in water contain- 

 ing a small amount of alkali (1/16 per cent, in case of polyhedra) 

 and are precipitated from this solution by acetic acid. The 

 nucleins which have a high phosphorus content are not decom- 

 posed by gastric juice, and are obtained as an insoluble residue 

 after the artificial digestion of nucleoproteins with pepsin. 



Since iron is an element known to be contained in chromatin it 

 was further thought advisable to determine whether the poly- 

 hedra during their synthesis from the chromatin and other 

 substances in the nuclei embodied any iron. It will be needless 

 to go through all the details of the analysis. Suffice it to say 

 that every precaution to prevent iron contamination from water, 

 air, etc., was used. Reagents known to be free from iron con- 

 tamination were employed. Furthermore, the polyhedra were 

 not rubbed with sand for fear of introducing iron in this manner. 

 .0988 of a gram of polyhedra were used and .00049 of a gram of 

 iron was found. 



On dissolving polyhedra in alkali and after dialyzing away 



