Mr. Rainey on the Structure of the Cysticercus cellulosse. 487 



multitude of small oval laminated calcareous bodies, which, when 

 acted upon by acids, effervesce briskly, and become partially dis- 

 solved, leaving only a small residue of animal matter. When the 

 neck is protruded, the extremity farthest from the cyst is seen to 

 present an enlargement, sometimes called the head, on the free 

 surface of which there is a quadrangular area, occupied by 

 four circular disks and a ring of booklets. Each angle contains a 

 disk, and the booklets are placed in a circle around the centre of 

 this space. The suctorial disks are traversed each by a passage 

 taking rather a spiral course, and terminating in the cavity of the 

 neck. The membrane composing a disk presents two orders of 

 fibres, circular and radiating. The booklets are generally twenty- 

 six in number, thirteen long and as many short, arranged alter- 

 nately a long and a short one. Each consists of a curved portion 

 like a bird's claw, and a straight portion or handle ; and at the 

 junction of these two parts there are tubercles, two in the short 

 booklets, and only one in the long ones. The booklets are crossed 

 by two zones of circular fibres. They are also connected by 

 radiating fibres, which occupy the spaces between each adjacent 

 pair, like the interosseous muscles situated between the metacarpal 

 bones and phalanges. The booklets are disposed like radii, with 

 their points turned outwards and the extremities of their handles 

 inwards, which, not meeting, circumscribe a circular space whose 

 centre corresponds to that of the quadrangular area before men- 

 tioned. At this part there is no perforation answering to an oral 

 orifice, but here the membrane is simply depressed so as to present 

 a conical hollow. By pressure upon the neck, this membrane can 

 be made to protrude in the form of a tongue-like process, to which 

 the handles of all the booklets are connected, so that when this 

 part in the living animal is made to move, the handles of the hook- 

 lets will be drawn in with it, and their points carried from the 

 entozoon, and thus made to penetrate the part to which it attaches 

 itself. These entozoa are chiefly found in the cellular intervals 

 between the muscular fibres, contained in an adventitious cyst 

 formed by the condensation of the surrounding tissues. No more 

 than one entozoon is ever met with in one cyst. 



Development of the Cysticercus cellulosse. 

 The earliest appearance of the incipient stage of the Cysticercus 

 cellulosce is a fusiform collection of small cells and molecules in the 

 substance of a primary muscular fasciculus, or immediately beneath 

 its sarcolemma. These cells, in this condition of the entozoon, 

 have only an imperfect or partial covering; however, they soon 

 become completely enclosed in a well-defined membrane which is 

 at first homogeneous, but which afterwards sends out short, 

 slender, projecting fibres, resembling short hairs or cilia. These 

 hair-like fibres, though resembling in some respects cilia, diflfer 

 from them in being much less sharply defined and less pointed ; 

 however, for convenience sake, I shall speak of them as cilia. 

 Their direction is remarkable. At either extremity of the fusiform 



