678 LECTURE XXIX. 



substance introduced is broken down, and in what form it leaves the body. 

 Conversely our interest is fastened upon the way in which the body reacts 

 toward the influence of certain compounds. Here also innumerable specific 

 cell reactions come into play, and we constantly meet with indications of 

 the functional differences of the cell-complexes of different organs. Investi- 

 gation in this field is only just beginning. We lack methods for tracing 

 the course of each individual substance in the body from cell to cell. We 

 should like to know whether the different body-cells have a different 

 affinity for certain products which are introduced, and whether perhaps 

 the specific reaction of the organism is not the expression of the ability for 

 selection on the part of certain particular tissue-cells. On the other hand, 

 we are interested, in every case, to know how the animal organism 

 wards off the action of all the different substances which are introduced 

 into the body and are foreign to it. In considering the functions of the 

 cells we constantly met with such problems and have seen in how many 

 different ways the organism protects its cells from the action of such sub- 

 stances. Sometimes the substance which is introduced is oxidized, some- 

 times it is reduced, and at other times it is conjugated either directly, 

 or after certain preparatory attacks, with different substances which 

 are produced in the intermediate metabolism. Thus we have seen how 

 the aniihal organism behaves toward glycocoll, sulphuric acid, urea, and 

 glucuronic acid. 1 We know that the proteins themselves play an impor- 

 tant part in these processes. They combine with many of these harmful 

 substances which are introduced into the body and form insoluble com- 

 pounds. Often this combination involves the breaking down of the 

 cell. The cell-albumin becomes incapable of exerting its function. The 

 effect of a great many poisons is due to their affinity to the proteins of the 

 cells and tissues. Here again we meet with certain specific differences 

 according to the nature of the cell and the proteins which have taken part 

 in their construction. In this connection we would recall the different 

 coloring of the cells, the cause of which is likewise attributed to a different 

 chemical construction of the cells. It is this which lies at the root of 

 the various functions of the different kinds of cells, and the separate 

 organs, and upon it depend also all of the various reactions which have 

 been mentioned, whether the cell plays an active part, or whether a 

 mere passive one. 



1 Cf. E. Fromm: Die chemischen Schutzmittel des Tierkorpers bei Vergiftungen. 

 K. J. Triibner, Strassburg, 1903. 



