ALIMENTARY TRACT: RECTUM 657 



more secondary branches ; while in the Argatini, at least in Ornithodorus, 

 there is in addition an antero-median and a true lateral branch. In the 

 Argatini the secondary branches are short, stout, and often very 

 irregular in outline ; in the Ixodini they are narrower and very much 

 longer, many of the secondary branches, which are difficult to unravel, 

 reaching as far as the brain. In both the Argatini and Ixodini peristaltic 

 movements are well marked in the mid-intestine, the blood being driven 

 into the diverticula. In the Ixodini the diverticula often exhibit a curious 

 appearance, being constricted in parts to form lobulations ; these are 

 also seen in the Argatini, but the lobulations are much larger, (in O. savignyi 

 for instance) so that the diverticula have a ballooned appearance ; at 

 first sight the alimentary tract appears to consist of a collection of cystic 

 bodies. 



The hi nd -intestine arises from the posterior surface of the mid-intestine 

 a little above its termination, either from its middle or from one side. 

 It is displayed either by cutting off the posterior diver- 

 ticula, or by reflecting them and then lifting up the post- Thfl hind-intestin. 

 , , , .,. . . ,. ,. . Plates LXXXIII and 



enor end ot the mid-intestine. 1 he hind-intestine will LXXXIV 



be recognized as a narrow tube passing downwards and 

 backwards to end on the posterior surface of the rectum. In O. savignyi 

 and O. moubata it consists of a delicate white cord and is functionless ; 

 it passes over the uterus and dips down below the rectum to end on its 

 posterior surface. In Argas persicus it is a much larger structure, is 

 broad at its origin from the mid-intestine, and narrows somewhat as it 

 passes down to end on the posterior surface of the rectum ; it nearly 

 always contains black digested blood and is in this tick a patent tube ; 

 this is demonstrated by the fact that an adult female, kept in a test 

 tube, passes out black faeces. 



In Margaropus and Hyaloinma the hind-intestine (Plate LXXXIV, 

 figs. 1,2, 4 and 5) is broad at its upper end, which often contains black 

 digested blood ; it soon, however, narrows down to a delicate cord at 

 its point of insertion into the rectum ; as in O. savignyi, it is functionless. 



The rectum lies in the middle line, about the junction of the middle 

 and posterior third of the body and just below the uterus. It may consist 



only of a single round sac or there may be in addition 



The rectum 



one or more secondary diverticula connected to the 

 main sac by narrow tubes. In Argas persicus (Plate LXXXIII, figs. 

 1 and 2; Plate LXXXIV, fig. 3) there is a large .central sac and two 

 diverticula ; both the main sac and its diverticula exhibit varying degrees 

 of .distension, but always contain black digested blood.. In Omithodorus 

 83 



