THE MALPIGHIAN BODIES OF THE KIDNEY. 
73 
Reflecting on this remarkable structure of the Malpighian bodies, and on their 
singular connection with the tubes, I was led to speculate on their use. It occurred 
to me that as the tubes and their plexus of capillaries were probably, for reasons pre- 
sently to be stated, the parts concerned in the secretion of that portion of the urine 
to which its characteristic properties are due (the urea, lithic acid, &c.), the Mal- 
pighian bodies might be an apparatus destined to separate from the blood the watery 
portion. This view, on further consideration, appears so consonant with facts, and 
with analogy, that I shall in a few words state to the Society the reasons that have 
induced me to adopt it. I am not unaware how obscure are the regions of hypo- 
thesis in physiology, and shall be most ready to renounce my opinion, if it be shown 
to be inconsistent with truth. 
In extent of surface, internal structure, and the nature of its vascular network, the 
membrane of the uriniferous tubes corresponds with that forming the secreting surface 
of other glands. Hence it seems certain that this membrane is the part specially con- 
cerned in eliminating from the blood the peculiar principles found in the urine. To 
establish this analogy, and the conclusion deduced from it, a few words will suffice. 
1. The extent of surface obtained by the involutions of the membrane, will by most 
be regarded as, itself, sufficient proof. But, 2. Its internal structure is conclusive. 
Since epithelium has been found by Purkinje and Henle in such enormous quantities 
on the secreting surface of all true glands, its use cannot be considered doubtful. It 
never forms less than ^-§ths of the thickness of the secreting membrane, and in the 
liver it even seems to compose it entirely, for there I have searched in vain fora base- 
ment tissue, like that which supports the epithelium in other glands. As I have 
endeavoured to show in the forthcoming Number of the Cyclopaedia of Anatomy, the 
epithelium thus chiefly forming the substance of secreting membrane, differs in its 
general characters from other forms of this structure. Its nucleated particles are 
never clothed with cilia, and are not surrounded with a definite cell-membrane. 
They are more bulky, and appear from their refractive properties to contain more 
substance, their internal texture being very finely mottled, when seen by transmitted 
light. In these particulars, the epithelium of the kidney-tubes is eminently allied to 
the best-marked examples of glandular epithelium. 3. The capillary network sur- 
rounding the uriniferous tubes is the counterpart of that investing the tubes of the 
testis, allowance being made for the difference in the capacity of these canals in the 
two glands. It corresponds with that of all true glands in lying on the deep surface 
of the secreting membrane, and in its numerous vessels everywhere anastomosing 
freely with one another. 
These several points of identity may seem too obvious to be dwelt upon, but I have 
detailed them in order to show, that in all these respects, the Malpighian bodies 
differ from the secreting parts of true glands. 1. The Malpighian bodies comprise 
but a small part of the inner surface of the kidney, there being but one to each tor- 
tuous tube. 2. The epithelium immediately changes its characters, as the tube ex- 
MDCCCXLII. 
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