252 OF THE FUNCTION 



ing the canal, while the former shortens it. Upon both 

 depends the very great and permanent irritability of the 

 intestines, formerly mentioned (300). 



The nervous coat is condensed cellular membrane, 

 easily reduced by handling or more particularly by in- 

 flation, into a spumous tela;* in it the intestinal 

 blood-vessels run to the mesenteric f in a beauti- 

 fully arborescent form;;}; the intestines, no less than 

 the stomach, are indebted to it for their tenacity and 

 strength. 



The interior, lined by its delicate epithelium, and de- 

 serving the name of villom in the small intestines more 

 than in any other part of the canal, forms, in conjunc- 

 tion with the inner surface of the former coat, here 

 and there, undulated ridges and rugous plicae, which, 

 in dried and inflated intestines, resemble the blade of 

 a scythe, and are termed the valvulae conniventes or 

 Kerkringhianae. 



408. The villi, which are innumerable || upon the 

 inner surface of the intestines, and whose beautiful and 

 minute vascular structure was first carefully investi- 

 gated, though described with exaggeration, by Lieber- 

 kiihn,* * may be, perhaps, compared, while destitute 



* B. S. Albinus, Annotat. Academ. L. ii. tab. iv. fig. 1, 2. 



f- Eustachius, tab. xxvii. fig. 2. 4. 



t B. S. Albinus, Dissert, de arteriis et venis intestin. hominis, with coloured 

 plates. LB. 1736. 4to. Also his Annotat. acnd. L. iii. tab. i. ii. 



Kerkring, Spicilegium anatomicum. tab. xiv. fig. 1,2. 



|| He estimated their number, in the small intestines of an adult, to be about 

 500,000. 



** De fnbrica et actione villorum intestinor. tenuium hominis. LB. 1745. 4to. 



J. Blenland, Descriptio vasatlornm intestinorum tenuium hominis. Ultraj. 



1797. 4to. 



R. A. Hcdwisr, Di.^nintiu mnpnllnnim Lidntrhi/hnii. Lips. 1797. 4to. 



C. A. Ru- 



