382 



LECTURE XVII. 



period of lactation. If the assumption be correct that the organism of 

 the mother ordinarily provides her young with sufficient iron before the 

 birth, and that the percentage of iron diminishes during lactation, it 

 would seem probable that in the case of guinea pigs there would be no 

 such maximum iron content at the time of birth, for there is no need of 

 such a supply, inasmuch as the animal immediately after birth begins to 

 feed on green fodder, which is rich in iron. In fact, as Bunge has shown, 

 this assumption is verified by the facts: 



Here, as we expected, there is no maximum of the iron content at birth 

 as compared with later periods; there is likewise no minimum. 



Why does the animal organism prefer, as a rule, to supply the new being 

 with such a store of iron at birth as will permit it to be satisfied with a low 

 iron content in the milk? Bunge's idea is that the assimilation of iron is a 

 difficult process. The organism of the mother is, therefore, as economical 

 as possible with its stores of iron, and prefers that the young should receive 

 it through the more certain path of the placenta than through the alimen- 

 tary canal of the offspring. 



The importance of the iron stored in the organism may, however, be in 

 another direction. First of all it is to be decided in what form the iron is 

 deposited in the new-born animal. We can, indeed, imagine that to some 

 extent at least it is present as an antecedent of hemoglobin, so that it can 

 be quickly changed into the latter as occasion demands. On the other 

 hand, it is also possible that the offspring is provided with a large amount 

 of hemoglobin itself. It is true that the naked, helpless being which de- 

 velops so rapidly after birth requires a large amount of oxygen to effect 

 the various oxidation processes which take place within it, and in order 

 to make use of all this oxygen it requires hemoglobin. The following 

 summary shows that, as a matter of fact, the amount of hemoglobin present 

 per kilogram of the body weight is greatest at the time of birth. 1 



1 Emil Abderhalden: Z. physiol. Chem. 34, 500 (1902). 



