1894.] MICROSCOPICAL JOURNAL. 167 



liian body " or the convoluted portion or the loops of 

 Henle are secreting or filtering parts, or are both, are 

 all of them unsettled questions. The peculiar " rodded" 

 structure of the cells of the convoluted tubule also calls 

 in vain for a satisfactory physiological explanation. 



It, remains, the problem of renal physiology, among 

 many other questions, to isolate the various elements and 

 to state clearly the respective functions of each, and the 

 conditions which govern it in the working body. In view 

 of the complexity of such a problem it is no wonder that 

 physiology is still in its infancy. 



It now remains for us to investigate the vascular and 

 supporting structure of the kidney. This will be facili- 

 tated if the student has injected material from which to 

 study. 



The main divisions of the renal artery enter, as already 

 noted, at the same place where the main renal duct, the 

 "ureter," leaves the organ. These branches pass beside 

 the pelvis of the organ, and, arriving at the "malpighain 

 pyramids," run radially beside the collecting tubules to 

 the level of the cortex where they branch sending ar- 

 terioles each way, both toward the centre in the " mal- 

 pighian pyramids " and out into the cortex. All the 

 capillaries from these as in all glands ramify between 

 the secreting regions of the organ. In this instance, 

 capillaries from the arteriole run into the "malpighian 

 corpuscles " where they form a capillary network and 

 then a single vein emerges. Both the entrance and exit 

 of these vessels is through the opening of the bulb which 

 leads to the first cavity, already shown not to be in re- 

 lation with the cavity of the tubule. Having come out 

 of the bulb, the vein breaks up again into a second set of 

 capillaries which surround in minute meshes the con- 

 voluted tubules and then collect again to run off, by way 

 of the " malpighian pyramids," to the renal vein. The 

 distribution of the blood is very clearly shown in figure 



