482 THE PHYSIOLOGY OF REPRODUCTION 



resulting in the production of a dark pigment, and they have 

 suggested that this reaction may be related to the special pig- 

 mentation of pregnancy. 



Removal of amino-growps from amino-acids. — Savarfe states 

 that the placenta transforms the NHg group of amino-acids into 

 ammonia by means of a special ferment, a desamidase. 



Decomposition of peroxides. — This reaction may be produced 

 by enzymes, the so-called indirect oxidases, and is sometimes 

 regarded as the means by which oxidation changes are re- 

 stricted to the appropriate parts of the body, and secluded, for 

 instance, from the blood (Leathes ^). The guaiacol reaction, by 

 which a colourless solution of guaiacol becomes red, takes place, 

 according to Charrin. and Goupil, when hydrogen peroxide is 

 present ; in other words, placental tissue decomposes the 

 peroxide, and the nascent oxygen oxidises guaiacol. Hofbauer, 

 however, says that the presence of hydrogen peroxide is not 

 required, i.e. that the placenta acts as a direct oxidase. 



Decomposition of glucose. — No glycolytic ferment is present 

 in the placenta.^ 



A few ferment actions still remain — e.g. the removal of urea 

 from arginin, the decomposition of uric acid, and the oxidation 

 of purine bases— which have not yet been investigated in the 

 placenta. 



V. General Considerations op Fcetal Nutrition and 

 THE Placenta 



A. The Plan of Placental Formation 



The problems of foetal nutrition are not new problems. They 

 deal with the assimilation of organic and inorganic substances, 

 and their incorporation in the developing tissues. These 

 phenomena are made up .of a series of chemical changes which 

 must be studied individually before we can hope to understand 

 the final sum which constitutes foetal metabolism, or the dis- 

 turbances which constitute fcetal disease. Set in the path 



' Leathes, Problems in Animal Metabolism, London, 1907. 

 ' It cannot yet be held as proved that glycolysis by ferment action occurs 

 at all in animals. 



