440 THE SOLIDS. 



be external to the cavity of the dilated extremity of the tube, 

 the relation between the two being comparable to the head 

 within the double night-cap. 



The correct view of the structure of the Malpighian body 

 is, however, much more simple than either of those just de- 

 scribed. A Malpighian body, as already stated, consists of 

 the dilated extremity of a uriniferous tube, over which is 

 spread the Malpighian plexus : these two structures, viz. the 

 dilatation of the uriniferous tube, and the vascular plexus, 

 constitute all that is essential in the anatomy of the Mal- 

 pighian body : both are inclosed in a thick capsule : this is 

 not, however, a structure peculiar to the Malpighian body, 

 but a mere envelope, similar to, as well as a continuation of, 

 that which invests the tubes themselves. 



A little reflection will show, that this view reconciles 

 many of the conflicting statements, made in reference to the 

 anatomy of the Malpighian body. The outer capsule referred 

 to, which is that spoken of by most other observers as the 

 true Malpighian capsule, is evidently that which Mr. Bow- 

 man had in view as the dilated extremity of the uriniferous 

 tube, and it is this which he described as being pierced by 

 the Malpighian artery, a description literally and positively 

 correct. 



The common envelope, which, however, as already stated, 

 forms no necessary part of the Malpighian body, is really 

 pierced by both the afferent and efferent vessels of that body, 

 as well as by the tube. (See Plate 60. fig. 3.) Mr. Bow- 

 man's error consists in having regarded this mere outer cover- 

 ing as the true dilated extremity of the uriniferous tube, which 

 it most certainly is not, and in having necessarily, as a conse- 

 quence, overlooked the true extremity of the uriniferous tube 

 with its contained epithelium. 



Again, the confounding of this common envelope with the 

 true Malpighian capsule accounts for the assertions of those 

 observers who state that the uriniferous tube has no con- 

 nexion with that capsule: it has, indeed, no connexion by 

 continuity; it simply pierces it: of the inner or true capsule, 

 the uriniferous tube is absolutely a continuation. 



