414 PATH TAKEN BY SUGAR. [Book n. 



appears in the portal blood during digestion is, for the most 

 part at least, not fat absorbed by the capillaries of the alimen- 

 tary canal but fat absorbed by the lacteals. Moreover, when 

 the chyle of the thoracic duct is diverted through a cannula, 

 and not allowed to flow into the blood, the quantity of fat in 

 the portal blood as in the blood at large is very small indeed. 

 Lastly, when a villus of an intestine in full digestion of fat is 

 treated with osmic acid, fat cannot be recognized by the micro- 

 scope within the capillaries or other blood vessels, though it 

 abounds outside them in the substance of the villus and in the 

 lacteal radicle. 



We may probably therefore infer with safety that all or at 

 least very nearly all the fat absorbed from the intestine takes 

 the path of the lacteals. As to the deficit mentioned above, 

 that is as yet without explanation. It may be that in some 

 way, on its course, in the lymphatic glands, for instance, the fat 

 is taken away from the chyle, hidden so to speak somewhere 

 away from both chyle and blood ; but on this point we have no 

 exact information. 



§ 248. Water and Salts. If, in an animal, the rate of flow 

 of lymph or chyle through a cannula placed in the thoracic duct 

 be watched, and water or, to avoid the injurious effect of simple 

 water on the mucous membrane, normal saline solution be then 

 injected in not too great quantity into the intestine, no marked 

 increase in the flow of chyle through the cannula is observed. 

 From this we may infer that the water of the intestinal contents 

 is absorbed not into the lacteals but into the portal system. If 

 however a very large quantity of the normal saline solution be 

 injected so as to distend the intestine, then the flow of chyle is 

 increased to some extent. It would appear therefore that 

 while under normal conditions the water passes from the intes- 

 tine mainly into the portal blood, some of it may under circum- 

 stances pass into the lacteals. 



With regard to the course taken by ordinary saline matters 

 we possess no detailed information. When special salts such 

 as potassium iodide and others, easily recognized by appropriate 

 tests, are introduced into the intestine, they may be speedily 

 detected both in the blood and in the contents of the thoracic 

 duct ; but whether, in such cases, these salts find their way into 

 the thoracic duct by the lacteal radicle of the villi, or pass into 

 the lymph stream at some later part of its course, we do not 

 know. Nor can we with regard to such a salt as sodium 

 chloride, state absolutely that it passes mainly with the water 

 into the portal blood, though we may fairly suppose this to be 

 the case. 



§ 249. Sugar. Both blood and chyle contain, normally, a 

 certain small amount of sugar ; and careful inquiries shew that 

 the percentage of sugar in chyle and in general blood is fairly 



