The Placenta as an Endocrin Organ 



FREDERICK S. HAMMETT 



PHILADELPHIA 



Early Views as to Placental Functions. The functions of the 

 placenta have been a subject of recorded interest since Aristotle appor- 

 tioned to this organ the property of conveying blood to the fetus. Galen 

 supplemented and extended this conception, proposing the theory that the 

 pure blood (venous) from the uterine vessels was mixed with Pneuma 

 (arterial) in the placenta and then served the fetal needs; the vegetative 

 functions, however, such as nourishment and growth, were relegated to the 

 liver. These views were retained until the 16th Century, when the ana- 

 tomical studies of Fallopio, and later Arantius, threw much light on the 

 relationships involved, the latter coming to the conclusion that the placenta 

 is the tissue wherein the processes of formation and purification of blood 

 take place preparatory to its utilization by the fetus. Further con- 

 tributions by Spigelius were followed by the masterly work of Harvey, 

 who classified the placenta as a digestive organ in which "succum alibem a 

 matre provenientem nutriendo fretui porro concoquit." With the ex- 

 pansion of the idea of a specific individuality in function for each tissue, 

 initiated by Cartesius, the filtration theory of placental function was 

 launched, to be later added to and supported by Haller through the appli- 

 cations of the then but slightly known principles of physical chemistry. 

 This investigator characterized the placenta as being a great organ of 

 filtration, and the custodian of the material being passed on from mother 

 to fetus. The further development into what to-day remains funda- 

 mentally our concept of placental function with respect to fetal nutrition, 

 has been admirably summarized and discussed in a monograph by Hof- 

 bauer (a), into which it is unnecessary to go. This brief historical resume 

 is sufficient to demonstrate that the placenta has long been an object of 

 serious study. 



The classification of the placenta as a secretory gland was probably 

 first made by Johannes Miiller, who called attention to the possibility of 

 its possessing other functions than those of intermediary metabolism 

 between mother and fetus. 



More Recent Views as to Placental Functions. The Placenta as a 

 Factor in Mammary Hyperplasia,. The obvious changes occurring in the 

 development of the mammary glands during pregnancy led to a series of 



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