PLASMATIC VESSELS OF SOMMER AND LANDOIS. 303 



tory system ; no ramifying side branches were to be seen ; at most a 

 few accessory branches have been described in the head, and the 

 suckers are indeed provided (Fig. 153) with a special vessel springing 

 from the above-described circular commissure. 



It is also true that now and then vessels are given off from the 

 longitudinal canals, and are sometimes hardly less important than those 

 just mentioned. This is the case, for instance, in Tcenia perfoliata, 

 as was noted even by Kahane. The vessels pass soon after their 

 origin into the cortical layer, where they ramify, and finally assume a 

 capillary character. 1 The " plasmatic vascular system " observed by 

 Sommer and Landois in Bothriocephalus latus, traces of which are also 

 found in Tcenia saginata, obviously belongs to this capillary system. 

 This, however, only refers to those vessels which pass under the so- 

 called " subcuticula," and are really vessels, for in his later work on 

 Tcenia saginata Sommer has evidently represented the lateral nerves as 

 part of this apparatus. The vessels are described as fine and very 

 thin-walled passages, which ramify peripherally as well as cen- 

 trally, and ultimately become united with the processes of connec- 

 tive tissue corpuscles. By means of these cells, and by means of some 

 of the pores of the cuticle, they come into communication even 

 with the external layer. An excretory apparatus, consisting of 

 wider canals, was observed by Knoch 2 and Botticher, 3 in young and 

 transparent living examples of Bothriocephalus latus, but its existence 

 has since been denied. 



The designation chosen by Sommer and Landois for the vascular 

 system which they have observed, and the description there given, leave 

 not the slightest doubt that they regard the canals in question as an 

 arrangement for nutritive purposes. This idea is thus a repetition, 

 although in improved form, of an opinion, which we have formerly 

 maintained, and still maintain, to be erroneous, although it has mean- 

 while found a representative in Blumberg. 4 It is true that, according 

 to the latter, it is not the whole of the surface of the body that serves 

 for the reception of nourishment and for its introduction into the vas- 

 cular system, but only the inner surface of the suckers, whose cuti- 

 cular pores are in connection with the spreading terminal processes of 

 the longitudinal canals. " The vessels form, especially at the base of 



1 [According to the observations published by Pintner and Fraipont, in the above- 

 mentioned memoirs, the behaviour of this capillary apparatus is very different from that 

 here described. Its tubes never form a network, but, singly or united in pairs, open into 

 the wider canals, and bear each a ciliated funnel at the outer end. The cilia like 

 lappets are never present in the interior of the tubes. K. L.] 



- Mem. Acad. imper. St. Petersbourg, t. v., No. 5, PI. ii., p. 38-38, 1862. 



a Archivf. pathol. Anat., Bd. xlvii., p. 370, 1869. 



4 Loc. cit., p. 39. 



