I50 



Changes after Feeding. — ^Very little change 

 occurs in the glands after feeding. They are for 

 the most part still quite full of secretion. Probably 

 a very small amount only of secretion is used 

 with each puncture. 



The Ducts. — The intra-acinar ducts vary in 

 Culicines and Anopheltnes. In Ciilicines they remain 

 narrow and tubular throughout the entire length 

 of the gland. In Anophelines they become large 

 spaces in both types of acini, but especially in the 

 clear type. The duct is lined throughout by a 

 clear homogeneous skeletal material, which is 

 continuous with a similar substance dividing the 

 cells of the gland from one another. Into the duct 

 the secretion-filled cell opens by means of a small 

 opening. 



The duct, after leaving the acinus, consists of 

 a thick-walled tube, with a central spiral thread 

 resembling the spirals in the trachea. The wall 

 is homogeneous, but contains many nuclei. 



The Malpighian Tubules. — The malpighian 

 tubules are tubular bodies with caecal ends, 

 which open into the hind- gut. The cells are 

 extremely large, being, next to the pericardial 

 cells, the largest in the body. Each cell contains 

 a large nucleus, and contains numerous large 

 granules, which stain feebly with haematein, but 

 powerfully with Heidenhain's haematoxylin. 

 Numerous fatty granules are also present. Each 

 cell is wrapped round a central lumen, the cells 

 being arranged alternately, so that a zig-zag 

 appearance is given in section. The inner portion 

 of each cell is markedly striated, the lumen being 

 thus bounded by a striated area. In relation 

 with these tubules, a large number of tracheae and 

 tracheal end-cells exist. 



