THE MALPIGHIAN BODIES OF THE KIDNEY. 
61 
The lines of their mutual contact may then wear the aspect of a highly delicate 
areolar tissue, connecting the capsule with the tuft. The cavity existing in the na- 
tural state between this epithelium and the tuft, is filled by fluid, in which the vessels 
are bathed, and which is continually being impelled along the tube by the lashing 
movement of the cilia. In the Frog, where alone I have as yet been able to see these 
wonderful organs in motion, they were longer than those from other parts of that 
animal, and extremely active. 
The tubes, on issuing from the Malpighian bodies, invariably become greatly con- 
torted. I have on one occasion seen two of them unite, and from their dichotomous 
mode of division, when traced up from the pelvis, there can be little doubt that this 
is constantly their disposition. I have never, in all my examinations, met with any 
appearance of an inosculation between different tubules. The tortuous tubes unite 
again and again in twos, and finally, under the name of pyramids of Ferrein, become 
straight, and converge towards the pelvis, forming the medullary cones or pyramids 
of Malpighi. The Malpighian bodies are imbedded in a kind of nidus formed among 
these convolutions, and are touched on all sides by the surrounding tubes. As the 
emergence of the tube from the Malpighian body can be seen only at one point, it is 
not wonderful that it should have been overlooked, and that the demonstration 
should have seemed clear, that the Malpighian bodies merely lie among the tubes, 
and have no connection with them. 
The blood, leaving the Malpighian tufts, is conveyed by their efferent vessels to the 
great renal reservoir, the capillary plexus surrounding the uriniferous tubes. This, 
in its general arrangement, resembles that investing the tubes of the testis. The 
vessels lie in the interstices of the tubes, and everywhere anastomose freely, so that 
throughout the whole organ they constitute one continuous network, lying on the 
outside of the tubes, in contact with the basement membrane. This plexus is inter- 
posed between the efferent vessels of the Malpighian bodies and the veins. 
The efferent vessels of the Malpighian bodies are always solitary and never inoscu- 
late with one another: each one is an isolated channel between its Malpighian tuft, 
and the plexus surrounding the tubes. They are formed by the union of the capil- 
lary vessels of the tuft, and emerge from its interior in the manner already explained. 
After a course of variable length they open into the plexus. Their size is various. 
In general, they are smaller than the terminal twig of the artery, and scarcely, if at, 
all, larger than the vessels of the plexus into which they discharge themselves. But 
where the Malpighian tuft is large, the efferent vessel is usually large also, and di- 
vides into branches before entering the plexus. This is eminently the case with those 
situated near the base of the medullary cones, where the medullary and cortical por- 
tions of the organ seem to blend. The efferent vessels from these large Malpighian 
bodies are often three or four times the diameter of those of the plexus, and take a 
course towards the pelvis of the kidney between the uriniferous tubes. They were 
formerly mistaken for tubes. They branch again and again in the manner of arteries, 
