296 ON THE STRUCTURE OF THE MALPIGHIAN BODIES 



resembling, in this respect, all the primary, unmetamorphosed tissues 

 with which I am acquainted. 



True cells are, however, to be met with here and there in the 

 Malpighian pulp. There is first to be observed a clear area, as of a 

 cavity, surrounding an endoplast ; the periplast forming the outer 

 limit of this clear area then acquires a more distinct definition (fig. 5), 

 and becomes recognizable as a cell-wall, from the remaining periplast. 

 Such complete cells measure from i-2500th to i-i 500th of an inch in 

 diameter. A further change is undergone by the periplast within and 

 around some of these cells ; granules are deposited, which are some- 

 times minute and colourless, sometimes, on the other hand, have a 

 deep-red colour and a considerable size, constituting the well-known 

 ' pigment-globule-cells ' of the spleen ; but I may remark, that I have 

 never been able to observe any blood corpuscles in such cells. 



If the Malpighian pulp be pressed out or torn with needles, it is 

 very readily broken up and diffused through the surrounding fluid. 

 We then find in the latter free endoplasts — endoplasts surrounded by 

 definite cell walls and cell cavities — and granule and pigment cells, 

 corresponding with the elements which were observed in the un- 

 injured tissue. That the free cells were not primarily independent 

 .structures, but have simply resulted from the breaking up of the 

 periplast along its lines of least cohesion, is evidenced, in a very inter- 

 esting manner, by such forms as are represented in fig. 6, where two 

 cells may be observed still connected by a bridge of periplastic (or as 

 it would here be called, in the language of the cell theory, ' inter- 

 cellular') substance, while the outline of a single isolated cell is still 

 irregular and granular, from the adhesion of particles of the periplast 

 of which it once formed a portion. Such bodies as these are quite 

 undistinguishable, structurally, from pus, mucus, or colourless blood 

 corpuscles.'- 



3. The Periplieral portion, so-called " Wall',' of the jMalpigliiau Body. 



In the human spleen, the Malpighian bodies cannot be said with 

 any propriety to possess walls. Their structure remains, as we have 

 described it, up to their junction with the surrounding red pulp. At 



■* The above account of the structure of the Malpighian bocUes is essentially identical with 

 that given by jMr. Wharton Jones, 1. c. pp. 34, 35, but was drawn ujd before I had the good 

 fortune to become acquainted with his article. He describes the wall of the nucleated cells 

 as being "not very smooth," and the periplast as a "diffluent intercellular substance," 

 whence I presume that I may quote him as an authority for the absence of fluid in the 

 Malpighian bodies. 



