THE STRUCTURE AND FUNCTIONS, &c. 5 



and the lacteals, when viewed by transmitted light, were of a light 

 brown colour ; but when examiued as opaque objects, they stood 

 out of a dead white appearance, contrasting strongly with the semi- 

 transparency of the surrounding texture. Repeated examinations 

 of these preparations satisfied me that Dr. William Hunter and Mr. 

 Cruikshank were quite correct in describing and figuring radiat- 

 ing lacteals within the villi, but that they \vere led into error in 

 describing those vessels as opening on the free surface of the gut, 

 partly by imperfect instruments and methods of observation, partly 

 by the general prejudice of the period in favour of absorbent 

 orifices. I also satisfied myself of what appeared highly probable 

 from the commencement of the observations, that the villi, when 

 turgid with chyle, were destitute of their ordinary epithelial 

 covering. This circumstance I could not avoid connecting with 

 the fact of the stomach throwing off its epithelia during the pro- 

 cess of digestion. I determined, therefore, to investigate the pro- 

 cess of absorption of chyle in fresh subjects, as the facts exhibited 

 in Mr. Cruikshank's preparations indicated the probable existence 

 of complicated processes going on in villi during digestion. The 

 analogy of the vesicular bulbous extremity of the villus, to the 

 spongiole of the vegetable, forced itself upon me, and the existence 

 of milky chyle, within closed cells, led me to anticipate an expla- 

 nation of some of the phenomena of digestion. 



A dog was fed. Three hours afterwards he was killed. The 

 lacteals were turgid, and the gut was found to be full of milky 

 chyme, with an admixture of thin brownish fluid of a bilious 

 appearance. The milky matter was situated principally towards 

 the mucous membrane ; the brown fluid occupied the cavity of 

 the gut. 



The white matter consisted of a transparent fluid, with a few 

 oil globules, and numerous epithelia. 



Some of the epithelia I recognised as those which cover the 

 villi. They were pointed at their attached extremities, flat at the 

 other. Many of them were single, others were united in bundles, 

 adhering principally by their flat or free extremities, as if a fine 

 membrane passed over and connected the edges of their extreme 

 surfaces. Occasionally these epithelia presented a distinct nu- 

 cleus ; but generally, and whether single or in bundles, they 



