448 



among which the grasserie prevails in a severe form are contaminated internally, and 

 their silk being impaired, are of less value. 



The internal alterations of a chrysalis affected with the grasserie are in all re- 

 spects identical with those found in the worm, and are principally in the blood, the 

 tracheffi, and the adipose tissue, which contain the characteristic polyhedral gran- 

 ules. It is a noteworthy fact that in some chrysalides that have died of the grasserie, 

 and whose organs are in a state of complete dissolution, the usual organisms of 

 putrefaction, i. e., micrococci and other bacteria, can not be found. 



It is known that before setting apart a lot of cocoons for the preparation of seed 

 among the precautions to be taken is that of examining the chrysalis in the cocoon. 

 If dead chrysalides are found, it will be highly important to determine the cause of 

 death. If death has resulted from mechanical lesions, which is rarely the case, the 

 chrysalis will not be dissolved, but wall be dried np, preserving here and there the 

 original color of its external covering. 



The case is different if the chrysalis has died of flaccidity or of the grasserie, be- 

 cause in both cases the internal organs pass into a state of complete dissolution, and 

 the body becomes black. In these conditions the disease cannot always be discov- 

 ered with the naked eye, and recourse should be had to the microscope. Chrysalides 

 that have died of the grasserie will contain the characteristic polyhedral granules, 

 while those that have died of flaccidity will show the presence of the usual organisms 

 of putrefaction, viz, micrococci and other bacteria. 



An examination of the symptoms of the grasserie shows that the principal one is 

 the spontaneous formation and multiplication of the polyhedral granules, which suc- 

 cessively invade all the tissues in a manner almost analogous to that of the corpus- 

 cles of the p6brine. We are not yet, however, in a position to decide whether these 

 granules are to be considered as an effect or as the cause of the disease.* 



The polyhedral granules of the grasserie were noticed first by Cor- 

 nalia,t who, however, did not discover their true form, which Vers- 

 son| determined to be crystalline, usually hexagonal, with very obtuse 

 angles. Bolle, while assistant to Haberlandt, studied their chemical 

 characteristics and the latter announced that they were crystals of 

 acid urate of ammoniiim^^ but Bolle himself in a later article,|| says that 

 he had been, in error in his first analysis, and that the urate found had 

 probably come from *'the derma of the worm and the adipose tissue of 

 the chrysalis," which existed as impurities in the deposit at first sup- 

 posed to be entirely composed of granules. The polyhedral granules 

 differ in appearance from the urate crystals found in the organs of the 

 worm and in the fluid excreted by the moth upon its exit from the 

 cocoon only in their size, the former being about 4/i in diameter while 

 the latter range from 0.5^ to 2//. Certain reactions upon these charac- 

 teristic granules of grasserie indicate an albuminoid nature, but the 

 fact that tbey have been retained for a year under water without 

 changing form refutes this supposition. 



Forbes 1] speaks of the granules as "evidently the mulberry cells and 



* Bolle, Annuario delV i. r. Istituto Bacologico Sperimentale di Gorizia, 1873, pp. 106- 

 114. 

 + Monagrafia del Bomhice del Gelso. 1856, pp. 348-351. 

 t Del Filugello et del suo allevamento, p. 141. 



^ Habej-landt, Sericoltura Austriaca, Anno. IV, No. 7. (April 1, 1872.) 

 |i 0}}. cit. 

 ^ iiulletin on the ^'Contagious Diseases of Insects^'' p, 279, 



