A New Conception of the Glomerular Function. 589 



ccelom. In the next stage of development that part of the body cavity which 

 contained the orifices of the renal tubules and the glomeruli became largely 

 constricted off from the rest, and by means of imperfect septa the glomeruli 

 also became partially separated from one another. This indicates that the 

 function of the glomerulus has now been restricted almost solely to work in 

 association with renal excretion. Later, this becomes entirely the case by the 

 complete separation of that portion of the ccelom from the rest. Each 

 glomerulus then works in conjunction with a renal tubule, but at first the 

 number of the latter is largely in excess of the former. The material 

 secreted at the glomerular surface is now conducted entirely to the tubule, as 

 is also any formed by the isolated portion of the ccelomic endothelium. It 

 is very significant that as soon as the relationship between glomerulus and 

 tubule is completed the latter loses its cilia, only the cells of the neck of the 

 tubule retaining them in some animals. This indicates that some other 

 mechanism for the propulsion of fluid down the tubule has taken the place of 

 the ciliary movement. This, according to my view, is the propulsive action 

 of the glomerular capillary loops. 



Previous Work Bearing upon the Subject. 



L. Hill, in discussing the general distribution of pressure through a soft 

 and yielding animal tissue, arrives at the conclusion that filtration is an 

 impossible mechanism at the glomerular surface. With much that Hill 

 expresses in his paper on " filtration in the Living Organism,"* I am in 

 complete agreement, but in several points I think he is incorrrect. Thus, 

 he considers that the glomerular capillary pressure must be transmitted in 

 undiminished amount throughout the whole renal tissue. This implies that 

 the wall of Bowman's capsule is incapable of offering any resistance to 

 extension, and similarly, too, for the walls of the tubule. Our measurements 

 show, however, that while these structures expand, they offer resistance to 

 expansion. They indicate that a higher pressure has been acting on the 

 internal surface of the tubule than on the outer, and especially until a 

 sufficient dilatation has been produced to make the kidney substance as 

 a whole expand, and thus render the Capsule tense. From that point on, 

 the tension in the kidney substance rapidly rises. I have found by measure- 

 ments of the blood flow that at this point the blood flow falls, due, that is, to 

 compression of the capillaries around the convoluted tubules and of the 

 renal veins. The fact that the capillary system which originates this 

 pressure consists of characteristic tufts which lie entirely within capsules 

 is very significant. In certain forms of tubular nephritis, in which the 

 * ' Biochem. Journ.,' 1906, vol. 1, p. 55. 



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