520 



MANUAL OF HISTOLOGY. 



We shall presently take into consideration their significance and bearing 



as regards the canals of the medullary substance. 



We may, if we like, look 

 upon the mass of the con- 

 voluted tubes, taken as a 

 whole, as divided into a 

 multitude of pyramidal 

 blocks by these groups 

 of straight passages, the 

 bases of the blocks being 

 directed towards the sur- 

 face of the organ. These 

 may be named, as Henle 

 has suggested, the " corti- 

 cal pyramids" 



Such a division, how- 

 ever, is artificial, as a cut 

 parallel with the surface of 

 the kidney shows (fig. 5 1 3). 



Fig. 513. Section parallel with the surface of the cortical por- 

 tion of the kidney of an infant (half diagrammatic), a, 

 transverse section of the urinif erous canals of the medullary 

 processes or radii ; 6, convoluted tubes of the true cortical 

 substance ; c, glomeruli and capsules of Bowman. 



Here we remark that the so-called cortical pyramids run into one another 



with the greater, part of their 

 lateral surfaces (b). 



Let us now turn to the con- 

 sideration of the convoluted tubes 

 of which the greater part of the 

 cortical mass is composed. 



Those whose diameter is on an 

 average about 0'0451 mm., un- 

 dergo no farther division ; their 

 outline is also single, and the 

 membrana propria possesses con- 

 siderable thickness, their outline 

 being in almost every case 

 smooth. 



The cells of the convoluted 

 tubes are also very characteristic 

 in appearance. Their bodies are 

 made up of granular cloudy pro- 

 toplasm, in which fatty molecules 

 are often imbedded, increasing 

 its opacity. In diameter they 

 range between 0'0099 and 

 0-0201 mm. (Scliweigg&r-SeideT). 

 Should the preparations have 

 been treated by the method most 

 generally in use at present, 

 namely, that of maceration in 

 hydrochloric acid, the convoluted 

 tubes will probably appear dark, 

 withoutany indication ofalumen, 

 and not unfrequently without 

 any distinct marking off of one gland cell from the other. 



The mode of termination of the uriniferous tubes is a point in regard 



Fig. 514. From the cortical portion of the human 

 kidney, a, arterial twig giving off the afferent 

 blood-vessel (6) of the glomerulus (c*, c 1 ) ; c, efferent 

 vessel of the latter; d, capsule of Bowman opening 

 into a convoluted uriniferous tube of the cortex e. 



