94 



SPECIAL HISTOLOGY. 



that when well injected, those whose epithelium has been 

 detached become coloured throughout ; and, in living 

 animals, or those which have just been killed, each villus, if 

 viewed from above, appears as a red dot surrounded by a clear 

 ring. In man, every villus contains a close network of 

 capillaries of 0003 — 0-005"', with rounded or elongated nuclei, 

 which lies immediately beneath the homogeneous external 

 layer of the matrix, and is supplied by 1, 2, or 3 small arteries 

 of 001 — 0*01 6'". The blood is usually carried back directly 

 into the larger trunks of the submucous tissue, by a vein of 

 0022'", which does not arise, as in animals, by the arching 

 round of the artery, but proceeds from the gradual confluence 

 of the finest capillaries. 



The relations of the lacteals in the villi of man, have not 

 hitherto been perfectly made out; for although the majority of 



„. onn investigators are inclined, like the older 



tig. 209. ° i , 



observers, to suppose that they com- 

 mence by one or two csecal branches, 

 yet recently, more and more voices ap- 

 pear to be raised for the view that they 

 originate in a plexiform manner. As to 

 my own opinion, I can affirm nothing 

 with respect to the human subject, since 

 I have never succeeded in meeting with 

 villi distended with chyle, and in empty 

 ones, I have been unable to obtain any 

 decisive evidence : on the other hand, 

 in animals, T feel certain that in many 

 cases only a single lacteal, which has 

 a csecal and frequently enlarged end, 

 and whose diameter is much greater 

 than that of the capillaries, traverses the 

 axis of the villus (fig. 209). 



For my own part in fact, I believe that 

 all the narrow cylindrical and filiform 

 villi will be found to present this con- 

 dition, but that, on the other hand, 

 the number and mode of origin of the lacteals may possibly 



Fig. 209. Two villi without epithelium and with the lacteal in their interior, from 

 the Calf, x 350, and treated with dilute solution of caustic soda. 



