598 LECTURE XXVI. 



namely, d-glucose. The cells of the liver take part in its formation, 

 inasmuch as they furnish the ferment which hydrolyzes glycogen. We 

 have already indicated that we must not regard these fermentation pro- 

 cesses as simple in their nature. Wherever it has been possible to follow 

 a fermentation closely, it has been found invariably that it consists of a 

 whole chain of separate processes. The ferment itself does not origi- 

 nally exist as such, but in a precursory stage, which is changed to the 

 active condition by the aid of a product obtained from other cells. We 

 cannot be wrong in assuming that such relations take part in the breaking 

 down of glycogen. 



We have mentioned these processes particularly because they seem 

 to be the most suitable for demonstrating how the different cells of the 

 body work together. It is certain that greater clearness would prevail 

 with regard to pathological processes if such relations were kept more in 

 the foreground in each instance and the diseased organ itself not so much 

 regarded as representing the whole " case." If we study all of the com- 

 plicated processes which take part in a single fermentation from the 

 beginning to the end, we shall realize at how many different places dis- 

 turbances in the normal course of metabolism may arise. 



Let us now return to the functions of the mammary glands. These 

 may very likely be excited into lactation by means of a secretion pro- 

 duced by the pregnant uterus, or its accessories. - The transformations 

 taking place in the dormant mammary gland from the beginning of its 

 preparatory period to the time when it enters into the full exercise of its 

 functions, are profound. There is an extensive formation of new cells. 

 The cells of these glands, which, like all other cells of the body, receive 

 their nutriment from the blood, suddenly make new demands upon 

 it. They abstract a great deal of material from the blood, which they 

 transform considerably. They form casein from the albumins of serum, 

 and lactose from d-glucose. Again the salts are removed in definite 

 amounts and quite independently of the ratio in which they are present 

 in the blood. We have previously gone into these details. How the 

 cells of the mammary glands accomplish these changes is not known. 

 We do not know of any intermediate stages between the serum-albumins 

 and casein, nor between grape-sugar and milk-sugar. We can merely 

 imagine that maltose is formed in the production of the latter. Before 

 much was known concerning the composition of the various different 

 proteins, the transformation of serum-albumin into casein did not appear 

 to be a very complicated process. To-day we are already compelled to 

 assume that before casein can be formed, the serum-albumin must be 

 decomposed to a considerable extent, after which a synthesis is effected. 

 The cells of the mammary gland do not in principle assume any extraor- 

 dinary position. Their chemism is merely an individual and a specific 



