566 E. H. DUSHAM 



LOCATION AND STRUCTURE OF THE GLANDS 



At the suggestion of Dr. W A. Riley, under whose direction 

 this work was carried out, the writer undertook to settle this 

 question. While the preceding investigations were made on 

 Periplaneta orientalis, yet a study of Blatta germanica showed 

 that smiilar conditions were present, and because of the abun- 

 dance of the latter, this species was used ahnost entirely in the 

 following work. 



In order to show the general distribution of the glands, the 

 abdomen was cut from the anterior part of the body, and a slit 

 through the chitin was made all around its margin, thus sepa- 

 rating the dorsal from the ventral wall. From these respective 

 parts the fat and muscle were removed as carefully as possible 

 so as not to injure the delicate hypodermis. It was found more 

 advisable to fix the entire abdomen before making the incision 

 around the edge, because the greater rigidity after fixation facili- 

 tated cutting, and prevented the parts from curling, as when 

 fresh material was cut. Both dorsal and ventral abdominal walls 

 were then stained with Grenacher's borax carmine and Delafield's 

 haematoxylin, and mounted in balsam. Better results were ob- 

 tained with the latter stain. The gland cells are so small that 

 they can hardly be distinguished from the normal hypodermis 

 except for the larger size of their nuclei, and these were rendered 

 more conspicuous by using Delafield's haematoxylin and destain- 

 ing with acid alcohol until the nuclei stood out prominently, 

 while the surrounding cytoplasm of the cells was but faintly 

 tinged. The nuclei are even better accentuated by dipping the 

 material in alkaline alcohol after destaining in acid alcohol, as 

 they take on a deep blue coloration after such treatment. 



As the glands are most prominent at the anterior portion of 

 each segment, and as this portion is covered by the posterior 

 part of the preceding segment, some difficulty was encountered 

 in making out their distribution. However, by injecting the ab- 

 domen with killing fluid by means of a hypodermic needle so 

 that the intersegmental membranes were stretched taut on a plane 

 with the rest of the tergite or sternite, all the glandular areas were 



