508 G. H. BERGOLD 



insoluble iii hot and cold water, alcohol, ether, chloroform, benzol, acetone, 

 etc. They are heavier than water: for example, B. mori polyhedra have a 

 density of 1.268 and Cacoecia murinana (Hbn.) capsules, 1.279 (Bergold, 

 1957). Polyhedra are clearly transparent, highly refractive, but not doubly 

 refringent, and, when dried, remain unchanged for years. Polyhedra and" 

 capsules are not destroyed by any of the natural putrefaction processes, but 

 dissolve in aqueous solutions of NaOH, KOH, NH3, H2SO4, and CH3COOH. 

 Staining is, therefore, greatly facilitated by pretreatment with acids (Escherich 

 and Miyajima, 1911). In heat fixed smears B. mori polyhedra are gram- 

 positive, but they become gram-negative after 2 hours treatment with 

 glycocolic acid at 60° C. Polyhedra of B. mori are not digested by papain 

 (at pH 8.3), trypsin (at pH 6.8), or pepsin (at pH 3.3-4.0), but they are by 

 pepsin at pH 2.0-2,9 and by trypsin and papain after alkali treatment: the 

 addition of cystein prevents inactivation by trypsin and papain of alkali 

 treated polyhedra (Zalmanzon, 1949, 1952). B. mori polyhedra are insoluble 

 in hemolymph of B. mori larvae (Bergold, 1943; Ishimori and Osawa, 1952; 

 Gershenson, 1956d), but seem to lyse in B. mori pupal lymph (Roegner-Aust, 

 1949) and in prepupae of Neodiprion sertifer (Geoffr.) (Krieg, 1955), which 

 might be due to an enzymatic mechanism rather than to an alkali. 



Verson (1872) first suggested the crystalline nature of polyhedra and found 

 that the B. mori polyhedra are mostly rhombododecahedra, but that cube- 

 shaped crystals occur, too. Polyhedra of L. monacha are usually tetrahedra 

 and those of Porthetria dispar (L.) are of irregular shape. The crystalline 

 nature of polyhedra w^as confirmed by preliminary X-ray investigations 

 (Bergold and Brill, 1942) and by direct demonstration of the macromolecular, 

 paracrystallme lattice, by electron microscopy (Morgan et al., 1955, 1956; 

 Day et al., 1956). Measurements taken from such electron micrographs of 

 thin-sectioned B. mori polyhedra suggested an ellipsoidal cross section of the 

 polyhedron protein molecule with major and minor axes of 79 X 52 A 

 (Morgan et al., 1955). However, an intensive investigation of a great number 

 of thin sections (Fernandez-Moran and Bergold, 1958) could not confirm this 

 finding but revealed a circular cross section with a diameter of about 70 A. 

 Considering the molecular weight, the length of the molecule should be 180 A. 

 The molecules are not in a hexagonal but in a simple cubic packing. The 

 cubic packing seems to be characteristic for all inclusion body proteins, 

 independent of the shape of the corresponding crystals. Since the cubic 

 packing is not the closest possible, one might assume differentiations on 

 the surface of the molecules with preferred spots of attraction. It is interesting 

 that the ellipsoidal capsules also show a crystalline lattice (Morgan et al., 

 1955; Fernandez-Moran and Bergold, 1958), and the examination of a great 

 number of capsules revealed that some capsules have developed one or several 

 sharp corners giving them an appearance similar to that of small polyhedra. 



