3G8 Illinois State Laboratory of Natural History. 



Some of the squash-bug nymphs sick with this disease, 

 or recently dead, were fixed in hot water, hardened, de- 

 liydrated, and imbedded in paraffin by the usual 

 process. Sections were then made, generally 6% a< in 

 thickness, with the idea of ascertaining as well as possi- 

 ble the general distribution of the bacteria within the 

 tissues. It is difficult to find stains that will differentiate 

 an organism under such circumstances. On finding that 

 anilines, haematoxylins, and combinations of these 

 worked to little advantage, Loffler's alkaline methylene 

 blue was tried with fairly good results. This was used 

 alone, or after previous staining with eosin. 



A few hours after the death of an insect, the tissues 

 are so badly broken down that little of interest is to be 

 gained from a study of such specimens. In sections 

 of an individual fixed just at the time of death, the 

 bacteria will be found in great abundance in all parts 

 of the perivisceral cavity and well differentiated from 

 the blood coagulum. (See Plate XXVII., Fig. 2.) The 

 blood, indeed, appears to have been like a pure cul- 

 ture of the disease organism. At this stage, moreover, 

 the adipose tissue and the hypodermis are considerably 

 broken down, and thoroughly penetrated bj' the para- 

 site. The cells of the cardiac tissue also show the pres- 

 ence of the bacteria; but the structure of these cells 

 and the form of their nuclei have suffered very slight 

 disturbance at this stage. There are very few structures 

 unattacked besides the muscles and the stout walls of 

 the alimentary organs; and surrounding both of these 

 the bacteria are often found in great abundance. 



Sections of a very sick nymph, killed probably not 

 more than an hour before death would have occurred 

 from the disease, show little that is different from the 

 preceding, except that the tissues are somewhat more 

 nearly normal. (See PlateXXVII., Fig. 3.) Another 

 nymph of the lot thus prepared was fixed while in a vei'y 

 early stage of the disease, the only sign of indisposition 



