400 LECTURE XVII. 



capable of making use of iron which is supplied in the form of highly com- 

 plicated organic compounds, or at least are unable to convert them into 

 such a state that they can be utilized for the formation of hematin. Per- 

 haps the preparatory decomposition in the alimentary canal has not taken 

 place, and thus the iron may circulate to some extent in the tissues, but in 

 a form from which the blood-forming organs are not able to set it free. 

 From this point of view, it is easy to understand the favorable action of 

 inorganic iron salts. Here we intentionally break away from the older 

 idea that the animal organism is dependent upon the nature of the food 

 that it receives. It is far more important that it receives all the materials 

 that it requires. The way these elements are originally combined in the 

 food is more or less a matter of indifference, provided they are susceptible 

 of decomposition. It is indeed this far-reaching decomposition and the 

 renewed construction which makes the animal organism to a considerable 

 extent independent of the kind of nourishment it receives. To be sure, 

 we must admit that apparently the animal cells are not capable of utilizing 

 certain kinds of combinations. Thus, it is improbable, for example, that 

 it is capable of constructing cholesterol, and perhaps not hematoporphyrin 

 from its simplest components, although it is precisely here that we meet 

 with the possibility that certain decomposition products of the albumins 

 may be utilized for the syntheses. At all events, we are not justified in 

 believing that hematogen and similar substances are necessarily direct 

 preliminary stages in the formation of hemoglobin. It is indeed possible 

 that these compounds contain all the necessary material for the formation 

 of the red pigment of the blood, although this has never been proved 

 directly. 



The theory we have thus developed concerning the action of inorganic 

 iron salts is not necessarily correct. By the addition of iron preparations 

 to the food, we increase the iron supply for the entire organism. It is 

 conceivable that this results in an indirect action upon the organs which 

 produce the blood. We know that widely different organs are intimately 

 related to one another in their metabolism and in the exercise of their 

 functions. In this connection, we need refer only to the regulation of the 

 sugar-content of the blood by means of the liver. Similarly the amount 

 of hemoglobin in the blood is a very constant quantity. Evidently we 

 have here another case of regulation. On the other hand, we have seen 

 also that the different ions exert a quite specific effect, and that it is, 

 indeed, possible for the predominance of one ion to cause a certain specific 

 action. It is conceivable that the heaping up of iron in the cells of the 

 body, and perhaps specially in the cells of certain organs, may give a new 

 impulse to the organs which participate in the formation of blood. 



The action of the " inorganic " iron was formerly attributed to a pro- 

 tective effect. Thus the sulphur in alkaline sulphides, instead of com- 



