varices they become loore and more replete with material and in- 

 crease in size until readily visible to the naked eye as red 

 graniiles already noted. In early stages of digestion, cells 

 packed with chromatin bodies and superficially resembling macro- 

 phages, the nat\xre of which is not clear, may be seen. 



Although a prominent part in digestion is taken by the free 

 cells just alluded to, epithelium lining the diverticula also 

 takes an active part in the process. The swollen and vaciJolated 

 portion of the large projecting cells is crowded with products 

 of digestion very much as is that of the free cells. Smaller 

 cells lying nearer the basement membrane are also, as a rule, 

 packed with fine black granules, though they rarely contain the 

 large graniiles seen in the other cells. 



The intensely black and opaque globules are highly charac- 

 teristic of digestion in the tick and undoubtedly represent the 

 ultimate condition to which blood remaining in the gut is reduced 

 by the digestive process. These globules probably represent only 

 the portion of food not assimilable, for in Ornithodoros ticks, 

 4Jhich may be kept alive for long periods without food, the diver- 

 ticula contain, after some weeks, an inky black material consis-U 

 ing entirely of these granules. 



As diverticula contents are digested, the muscle fibres, 

 which in the fully distended organ slightly indent the surface, 

 sink more and more into the body of the viscus. The wall between 

 the fibres becomes ballooned and eventually forms flasklike pock_ 

 ets with only a narrow opening connecting with the lumen. The 

 epithelium is, as a rule, present in the pockets, though it is 

 generally nore noticeable on the ridges formed by the contracted 

 muscTilar fibres. Remains of ingested blood, in the form of black 

 granules, are present both in the pockets and in the liimen. Ticks 

 examined ncnths after a meal still have the diverticula loaded 

 with the black material. 



Waste matter is not passed into the rectum and any remnant 

 of food not absorbed must remain"T n ~the diverticula until death 

 oT the tTclc . The method by which absorption takes place has not 

 ■BeelT^scertained . Black pigment is not detected in the tissue 

 cells or in the body cavity. Note that excess fluid in the blood 

 is excreted by the coxal organ dioring and following feeding so 

 that a large ancunt of blood can be rapidly ingested; this is 

 elucidated in the section on the coxal organ below. 



- 170- 



