Ill LYMPH 119 



these facts will become apparent when we speak of the 

 probable mode of formation of lymph. While lymph thus 

 differs in composition when derived from various parts of 

 the body, it also differs when collected from the same part 

 at different times. Usually the difference is slight, but in 

 the case of one source it is marked and important. In a 

 fasting animal the lymph coming from the intestines is 

 essentially the same as average lymph ; but after food 

 has been taken, and especially if the food contains 

 much fat, and food always contains some fat, this lymph 

 appears to be quite white or "mUky." Owing to the 

 thinness of the walls of the lymphatics the contents 

 are visible from their exterior, so that the vessels also 

 appear white or mUky, and hence this particular set of 

 lymphatics is known as the lacteals, and the contents 

 are called chyle. The only difference between chyle and 

 the lymph ordinarily present in the lacteals is that chyle 

 holds in suspension a large amount of fat (from 5 to 15 

 per cent.) in a state of extremely fine division. These 

 minute particles of fat reflect a great deal of the light fall- 

 ing upon them and hence the fluid appears white. Some 

 of the fat in chyle exists in the form of minute g'.ol)ules, 

 similar to those present in mUk, but the larger part is so 

 finely divided that it can only be spoken of as " gran- 

 ules " and in this form is known as the molecular basis of 

 chyle. 



13. The Mode of Formation of Lymph. —In all which 

 we have so far said respecting lymph we have spoken of it 

 merely as an exudation of fluid from the walls of the capil- 

 laries. The word '' exudation " was used purposely, as not 

 imjjlying more than that some of the liquid part of the 

 blood passes out into the tissues, and certainlj^ as not ex- 

 pressing any view as to the nature of the processes con- 

 cerned in that passage. But now that we have dealt with 

 the composition of lymph, and especially since we have 

 seen that the composition varies according to the part of 

 the body from which it flows, we may profitably con- 



