9 8 



NINTH LECTURE. 



The human corium projects in microscopically small papil- 

 lae, which the thick epithelium (p. 32) surrounds with a 

 smooth surface. The greater part of these papillae contains 



a capillary vessel, which ascends on one 

 side, bends over the top of the papilla, 

 and descends on the other side. This is 

 the capillary loop. 



Larger papillae occur on many of the 

 mucous membranes ; thus, on the dorsum 

 of the tongue, as the so-called gustatory 

 papillae, the whole small intestine, as intes- 

 tinal villi, to omit others. The simple 

 capillary loops are here no longer suffi- 

 cient (Fig. 95). Between them are inter- 

 posed communicating capillaries and capil- 

 lary net-works. Thus arises the looped 

 net-work. 



A quite peculiar formation is presented 

 by the cortical layer of the kidney, in the 

 so-called glomerulus or vascular coil (Fig. 

 96). 



A microscopic arterial branch (to the 

 right) divides, and each branch forms a 

 convolution of closely crowded capillaries. 

 These portions, with educting canals, reunite, at last, into a 



single abducting vascular tube. 

 We here speak, therefore, of a 

 centripetal (vas afferens) and a 

 centrifugal vessel (vas efferens). 

 From the" latter arises, further 

 below, a new capillary reticulum. 

 To study the capillaries, they 

 must be injected from the larger 

 trunks with transparent, colored 

 (with carmine, Prussian blue) gel- 

 atine, at an elevated temperature. Opaque, granular masses 

 (cinnabar, white lead, chrome yellow) were the more imper- 



Fig. 95. — An intestinal vil- 

 lus ; a, the cylindrical epi- 

 thelium with its thickened 

 seam : b, the capillary net- 

 work ; c. longitudinal layers 

 of smooth, muscular fibres ; 

 li, central chyle vessel. 



Fig. 96. 

 ney. 



-Glomerulus of the hog's kid- 



