548 THE TISSUES. 



larger branches finally terminate in the wider arched venous rami- 

 fications encompassing the pyramids (lobules). The veins of the 

 latter commence in a beautiful plexus surrounding the orifices of 

 the uriniferous tubes on the papillae, and, ascending with the arte- 

 ries of the pyramids between the tubuli recti, also terminate in the 

 ramifications just named. 



There are, proportionally, but few lymphatics in the kidney, ac- 

 companying the bloodvessels as far as the interlobular branches. 



The nerves also (from the cardiac plexus) form a plexus around 

 the arteries, to their interlobular subdivisions. How and where 

 they terminate is unknown. 



Of the chemical composition of the kidney but little is known. 

 Frerichs found from 72 to 73.70 per cent, of water, and 28 to 26.30 

 of solid matter. The fat amounted to from .63 to 1 per cent., or 

 even 1.86 (Owen Rees)\ but the greater part of the solid residue is 

 probably albumen from the epithelial cells (p. 114, 1). Dr. Beale 

 finds 76.45 of water, and 23.55 of solid matter ; viz., fatty matter 

 containing much cholesterine, .939; watery extractive, 5.84; fixed 

 alkaline salts, 1.01; earthy salts, .396; albumen, vessels, &c., 15.365. 



Function of the Kidney. 



The kidney secretes the urine ; for an account of which see pages 

 214-22. 



It is pretty certain that much of the water in the urine is merely 

 a transudation from the Malpighian bodies; while the peculiar ele- 

 ments of this secretion are secreted by the epithelial cells of the 

 uriniferous tubes, and mainly at least of the contorted portion. It 

 is, however, not probable that a rupture of the epithelial cells is 

 necessary, that their contents may become free in the straight por- 

 tion of the uriniferous tubes; and hence the same cell may continue 

 to secrete longer than has usually been supposed. (T. and B.) 1 



Development of the Kidney. 



The urinary passages are developed as an offset from the lower 



extremity of the intestine; the kidneys being solid at first, like the 



salivary glands. The tubuli are at first composed solely of a solid 



series of cells, without any basement-membrane. Subsequently the 







1 Dr. Isaacs, of this city, has recently read a paper before the New York Academy 

 of Medicine, maintaining that the urine is secreted also by the Malpighian bodies. 

 As it is not yet published, we cannot state the grounds of this opinion. 



