526 CHYLE. [BOOK n. 



probably comes from the bile poured into the intestine during 

 digestion ; but this is not certain. How far the nature of the fat, 

 that is, the proportion of the various kinds of fat, of stearin, &c., 

 varies with the fats present in the meal has not been definitely 

 ascertained. 



The condition of the fat in chyle is peculiar. Some of it 

 exists, like the fat in milk, in the form of fat globules of various 

 sizes, but all small. A very considerable quantity however is 



E resent in the form of exceedingly minute spherules or granules, 

 ir smaller than any globules to be seen in milk ; these exhibit 

 active 'Brownian movements/ The fat present in this form is 

 spoken of as the ' molecular basis ' of chyle, and is very distinctive 

 of chyle. In the emulsified contents of the intestine, often called 

 chyle, the fat is finely divided, and to a large extent into small 

 globules, but there is nothing corresponding to this molecular 

 basis ; the fat does not assume this condition until it has passed 

 out of the intestine into the lacteals. Lymph examined with the 

 microscope shews besides the white corpuscles only very few oil- 

 globules, and nothing of this molecular basis. 



The total amount of lymph or of chyle which enters the blood 

 system through the thoracic duct, though it probably varies con- 

 siderably, is probably also always very large. It has been calculated 

 that in a well-fed animal a quantity equal at least to that of the whole 

 blood may pass through the thoracic duct in 24 hours, and of this 

 it is supposed that about half comes through the lacteals from 

 the abdominal viscera, and therefore to a large extent from food, 

 and the remainder from the body at large. These calculations are 

 based on uncertain data, and cannot therefore be taken as of exact 

 value, but we may use them for the sake of an illustration. Thus 

 in a man of average weight, that is, about 70 kilos., the quantity 

 of blood ( 38) being -^ of the body weight is about 6 kilos. 

 The quantity of lymph or chyle therefore discharged into the 

 blood in an hour would be according to this calculation a quarter 

 of a kilo, or something less than a quarter of a litre ; and since the 

 flow must vary considerably in the 24 hours, would be therefore 

 sometimes less and sometimes even more than this. 



The Movements of Lymph. 



300. Making every allowance for the uncertainty of the 

 calculation detailed in the preceding paragraph, it is obvious that 

 the lymph must flow with a not inconsiderable rapidity (if we take 

 about half the above estimate, the rate will be about 1 or 2 c.c. 

 per minute) through the thoracic duct, and therefore must also be 

 continually streaming into that duct, along the various lymphatic 

 channels from the manifold lymph-spaces of the body. This 

 onward progress of the lymph is determined by a variety of 



