BLOOD AND LYMPH. 575 



and thus creates new conditions, so that one effect follows another 

 at the most rapid rate imaginable. It would not be right for us to 

 be satisfied with the bare explanation that the activity of the cell 

 is of a specific nature. Of course further investigations must have 

 free play here. It would be equally wrong to disregard the uncer- 

 tainty which systematic explanatory experiments encounter. Just as 

 it is incorrect to maintain that a chemical process prevails in the organ- 

 ism because it is possible to carry out certain processes in a test tube, 

 so also we are not justified in assuming that we have established the 

 fact that a purely physical process takes place because, under certain 

 definite conditions, we can in this way find a possible cause of a certain 

 phenomenon. It must be perfectly clear with each advance in the 

 knowledge of the processes taking place in the animal organism just 

 where the certainty exists and where it ceases. There is no doubt that 

 the assumption of a specific secretion being produced by the individual 

 cells has given rise to an uncomfortable feeling of insecurity in our 

 entire representations of the life processes. An advance in the science is 

 only possible when the gaps which still exist in our present information 

 are circumscribed as sharply as possible. For this reason we shall not 

 attempt to trace the formation of lymph and its metabolic exchanges 

 between the blood and the tissue-cells in accordance to physico-chemical 

 laws. 



We should like first of all to abolish any idea that the lymph-stream is 

 analogous to the blood-stream and carries the substances it contains 

 from cell to cell. The lymph circulates far too slowly for it to be able 

 to replenish the cells quickly enough with the material which they need 

 in cases of active metabolism. We must rather assume that the lymph 

 of a given organ enters into more intimate relations between the blood- 

 vessels and the surrounding tissue. G. von Bunge l has called our atten- 

 tion to an observation which well characterizes these relations. The milk 

 of animals whose young grow rapidly is very rich in lime. The milk of 

 dogs contains from four to five grams of lime per liter. A bitch weighing 

 20 to 30 kilograms will secrete half a liter of milk in 24 hours which will 

 contain from two to two and one-half grams of lime. A liter of plasma 

 contains only about 0.2 gram of lime, or only T V to ^ as much as the same 

 volume of milk. If, however, the epithelial cells of the mammary glands 

 must obtain their material for the milk requirements from the transu- 

 dated plasma, then during the 24 hours, at least 10 liters of plasma must 

 flow through the mammary glands. This is altogether out of the ques- 

 tion, for only one or two liters of lymph flows through the entire body in 

 the course of a day, and far less through the mammary glands. It 



1 Lehrbuch der Physiologic des Menschen, Vol. II, p. 289 (1901). 



