THE MUTUAL RELATIONS. 329 



every case there is enough fat already present to explain these fat 

 accumulations. 



Considering all the results of physiological and pathological experiments 

 with regard to the formation of fat from albumin, we must admit that 

 up to the present time no proof has been found which compels us to 

 assume a transformation of albumin into fat. We must not neglect to 

 remark that, although the fat present in the body is sufficient to explain 

 the accumulations of fat, still, this fact does not preclude the possibility 

 of its production from some other substance. We arrive at the above 

 indirect conclusion as it seems most probable to us. We would, however, 

 be making a grave error were we to consider the problem of the produc- 

 tion of fat from albumin as finally solved. Our comments only go to 

 show that the experiments and methods so far utilized are insufficient 

 to confirm such transformation. New questions and new points of view 

 are necessary for this problem. 



We have now reached the end of our observations concerning the con- 

 version of one substance into another. In the animal organism we are 

 absolutely certain only of the production of fat from the carbohydrates. 

 The reverse process, as well -as that of the production of sugar from albu- 

 min, has not yet been sufficiently demonstrated to warrant any definite 

 decision. At any rate, it will be necessary to look for some other source 

 than the carbohydrates for an explanation of the elimination of sugar 

 during severe cases of glucohemia. We have developed the assumption 

 that both fat and albumin must be taken into consideration, and that the 

 great differences of causes of glucohemia may correspond to different 

 origins of sugar. Finally, we have seen that there is no absolute proof 

 that the formation of fat is at all related to the presence of albumin. 



We have intentionally avoided giving any definite opinion on these 

 important questions, preferring to take the opposite stand corresponding 

 to uncertainty of the facts in hand. Nothing can hurt the progress of 

 knowledge more than the desire to reach conclusions on such complicated 

 questions from purely theoretical considerations. We are greatly indebted 

 to E. Pfliiger, whose critical observations have been followed in every 

 case where it seemed as if the question had been positively answered. He 

 has considered all the previous experiments, and has to a certain extent 

 repeated them. 



The relations are evidently entirely different in the plant. It must 

 manufacture its carbohydrate, fat and albumin, all from the same raw 

 materials. It easily converts carbohydrates into fats, and fats into 

 carbohydrates. It also undoubtedly synthesizes its albumin from sugar 

 and its derivatives. The future can alone decide whether there is any 

 marked fundamental difference between the activities of the plant and 

 animal cells, or whether any difference between them may be only quan- 



