202 W. K. BLOOK 



the living animal with considerable exactness. The result lias been an 

 accumulation of data from which we can now begin to get an insight into 

 the history of the fats after they leave the intestine. After absorption 

 that part of the food fat which has passed into the lacteals finds its way 

 into, the blood stream by way of the thoracic duct in the form of a sus- 

 pension of very tine particles (generally less than 1 H in diameter), in 

 which the Brownian movement is marked and which give the chyle and 

 the blood plasma their milky appearance. The milkiness persists for some 

 time but has generally disappeared in from eight to fourteen hours after 

 the fat is eaten. According to present observations milkiness persisting 

 fourteen hours after a meal indicates an abnormality in fat metabolism. 

 Emulsified fat (particles 2 to 5 u. in diameter) injected directly into tlio 

 veins disappears within a few 'minutes, the difference from alimentary 

 lipemia being due probably to the larger size of the fat particles, although 

 there is a possibility that the relatively small amount injected would be 

 quickly removed and stored while a larger amount would not Rabbeno 

 found that homogenized fat (particles up to 2 u. in size) injected in 

 quantity disappeared rather slowly (7 hours). The extent and duration 

 of the increase of the blood fat following a meal depends on the amount 

 of fat fed and also apparently on the level of the blood lipoids at the 

 time of feeding. When the blood lipoid level is high the maximum in. 

 the blood is reached sooner and the fall from the maximum is slower than 

 is the case when the lipoid level in the blood is low. The amount of extra 

 fat in the blood does not, however, at any time represent the amount 

 which has disappeared from the intestine so that absorption by the tissues 

 from the blood must normally be rapid. The extent of alimentary lipemia 

 varies greatly in different animals. In rabbits it is very difficult if not 

 impossible to produce. In geese stuffed with rye values as high as 6 per 

 cent have been recorded. This is probably a cumulative value, since under 

 these conditions fat absorption must be continuous. In dogs the blood 

 fat values rarely exceed three per cent, and in humans two per cent. In 

 human beings with diabetes, lipemia, which is probably primarily of ali- 

 mentary origin, with values of over 20 per cent, has been recorded, and 

 whilo this is an extreme instance, high values are not uncommon in un- 

 treated cases. The passage of fat from the blood is probably inhibited 

 in these cases, since on a low calorie low fat diet it may take a month for 

 values to get down to normal. 



The mechanism of the disappearance of fat from the blood is uncertain. 

 Stained or otherwise distinguishable fat injected into the circulation dis- 

 appears promptly as indicated, and is found to have accumulated in the 

 liver, bone marrow, spleen and muscles in the order named which is true 

 also of other finely suspended material of other kinds. During fat diges- 

 tion the fine fat particles are found to have accumulated in various places 

 along the endolhelial lining of the blood vessels. Various theories have 



