SACBROOD. 



17 



The ventral surface of these two thirds (fig. 16, PL II, o) is less con- 

 vex from side to side. The ridges and furrows, representing the seg- 

 ments, are less pronounced. The lateral margins are still deeply 

 notched. The prominent angle seen on the ventral side of a healthy 

 larva, at the juncture of the middle and posterior thirds, has given 

 place to a wider one in this stage of decay. The clear subcuticular 

 fluid frequently observed at the lateral and posterior margins of lar- 

 vae dead of this disease is here increased in quantity. 



Consistency of the contents of the sac. — The cuticuiar sac is now 

 more readily observed and less easily 

 broken. The decaying contents con- 

 sist of a more or less granular-appear- 

 ing mass suspended in a watery ap- 

 pearing fluid, the mass possessing a 

 slightly brownish hue. The micro- 

 scopic examination shows that the 

 granular appearance is due to the 

 presence of decaying tissue cells, 

 chiefly fat cells, which are changing 

 slowly as the decay of the larva goes 

 on. 



Condition of the virus. — The results 

 of inoculations show that the remains 

 of larvae at this stage of decay are 

 still in some instances infectious. The 

 amount of infection produced when 

 such larvae are used in making in- 

 oculations is very much less, how- 

 ever, than when larvae in the first 

 stage are used. 



Third Stage. 



Fig. 18. 



Third stage: Larva dead of sacbrood, 

 ventral view. (Original.) 



The color of the dead larva of this 

 stage is quite brown, that of the an- 

 terior third being a deeper shade than 

 that of the other two thirds. An indication that the remains are 

 drying is observed in the wrinkling of the surface that is beginning to 

 be in evidence. 



Anterior third. — The color of the anterior third is a deep brown. 

 This third still preserves its conelike form (figs. 17 and 9; PL II, j), 

 the distance of the apex from the roof of the cell being still further 

 increased. This may equal one-fourth or more of the diameter of the 

 mouth of the cell. The surface markings are still quite similar to 

 those of a healthy larva with the exception that evidences of drying 

 are present. 



58574°— Bull. 431—17 3 



