

THE LYMPH AND CHYLE. 371 



others are all intermittent in their action, and depend for their effi- 

 ciency upon the existence of valves in the lymphatic vessels. In a 

 set of vessels provided with such valves, opening forward and shutting 

 backward, any force which alternately compresses and releases them 

 will necessarily cause the fluids which they contain to move in a definite 

 direction. The mechanical forces above enumerated are more or less 

 constantly active, and in point of fact exercise a considerable influence 

 in producing an incessant transportation of the lymph from the peri- 

 phery to the centre. 



Total Daily Quantity of the Lymph and Chyle. The quantity of 

 fluids discharged from the thoracic duct within a given time varies 

 according to the condition of abstinence or digestion. In the fasting 

 condition it is comparatively moderate, but becomes more abundant 

 soon after the commencement of digestion, to diminish again during 

 the later stages of the process. We have found, at various periods after 

 feeding, in the dog, the following quantities discharged per hour, for 

 every thousand parts of the bodily weight of the animal : 



HOURLY QUANTITIES OF LYMPH AND CHYLE IN THE DOG, 

 PER THOUSAND PARTS OF BODILY WEIGHT. 



3| hours after feeding 2.45 



7 2.20 



13 ....... 0.99 



18 1.15 



18 " ...... 1.99 



It would thus appear that the hourly quantity of these fluids, after di- 

 minishing during the latter stages of digestion, increases again somewhat 

 about the eighteenth hour, though still considerably less abundant than 

 while digestion is in active progress. It is probable that this increase 

 at the two periods indicated is owing to two different causes. The fluid 

 obtained in greatest abundance in the dog, in from 3 to 1 hours after 

 feeding, is quite white and opaque, and its increase in quantity is evi- 

 dently due to the admixture of chyle absorbed from the intestine. That 

 obtained so late as the eighteenth hour is simply opaline, or more nearly 

 transparent, and is composed of lymph alone. The absorption of chyle, 

 therefore, takes place, of course, while digestion is in progress ; but the 

 most abundant production of lymph occurs some hours later, after the 

 materials of nutrition have reached and permeated the tissues themselves. 



The entire daily quantity of lymph and chyle is found, by direct 

 observation, \o be much larger than would be anticipated. In two 

 experiments upon the horse, extending over a period of twelve hours 

 each, Colin 1 obtained from the thoracic duct in this animal, on the 

 average, 893 grammes of fluid per hour, which would amount to rather 

 more than 20 kilogrammes per day. In the ruminating animals, accord- 

 ing to the same observer, the quantity is still greater. In an ordinary 



1 Physiologies comparee des Animaux domestiques. Paris, 1856, tome ii. p. 106. 



