ON THE INTKSTINAL VILT.T. 401 



terior to tlie organism. The second will include those which 

 present themselves after the alimentary matter is taken up 

 into the animal body, and becomes buried in its substance. 

 The first group of processes are mechanical and chemical in 

 their nature. They may be considered in a great measure as 

 peculiar to the animal, although even vegetables throw out 

 from their roots matter which, <icting on some of the materials 

 of the surrounding soil, prepares these for absorption. 



The second group of processes is common to animals and 

 vegetables. In these, for the first time, are alimentary sub- 

 stances taken into the tissues of the oi-ganism. In animal.s, 

 as in plants, as I have already pointed out, these alimentary 

 substances are drawn by a peculiar force into the interior of 

 the cells, after escaping from which they pass on by the ab- 

 sorbent system. The chemist has not yet informed us of the 

 change which the matter has undergone during its passage 

 from the cavity of the gut, or from the soil, into the afferent 

 lacteals and the sap-vessels ; but if in vegetables, as in 

 animals, this matter passes into the cavities of the cells of 

 the spongiole before it passes on to the sap- vessels, then it is 

 highly probable that the organising and \'italising part of the 

 function of digestion commences in the cells of the spongiole 

 and of the extremity of the villus. 



The extremity of the fibril of the root of a plant elongates 

 by the cells added to its ti.ssue by the germinating spongiole. 

 The spongiole is, therefore, an active organ of growth as well 

 as of absoi-ption. It is to the fibril of the root, what I have 

 denominated in the animal tissues the nutritive centre. I 

 conceive it to be probable, therefore, although as to this I 

 have made no observation.s, that absorption by, and elongation 

 of, the fibril of the root, var}' inversely a.s one another. This 

 supposition is founded on the a.ssumption that the cells of the 

 spongiole do not absorb by tnmsmis.^ion, but by growth and 

 solutiun. 



2d 



