572 THE PHYSIOLOGY OF REPRODUCTION 



Kirkness, 1 carried out a series of experiments upon guinea-pigs. 

 The mammary glands were removed prior to pregnancy (four 

 cases) or during pregnancy (one case). The urine was tested 

 for sugar both before and after parturition, but none was found 

 in any of the experiments. Other experiments showed that 

 glycosuria may occur after parturition in normal unoperated 

 animals, but that it does not do so invariably. 2 When glycos- 

 uria does so take place, its occurrence is probably comparable 

 to post-operative glycosuria, the cause of which is not under- 

 stood. The glycosuria observed by Porcher after the removal 

 of the mammary glands during lactation may perhaps be 

 explained as an ordinary post-operative effect, and cannot be 

 cited as proof of Bert's hypothesis. 



According to Thierfelder 3 and Landwehr, 4 a formation of 

 lactose may take place if pieces of fresh mammary tissue are 

 kept in normal salt solution at body temperature. The lactose 

 is said to be formed from a precursor which Landwehr identified 

 as " animal gum " or carbohydrate of low reducing power. 



According to Foa, there is a diminution of glucose in the 

 venous blood coming from the mammary glands, but the amount 

 of glucose and other carbohydrates present in the blood during 

 lactation is no greater than in normal blood. 5 



Muntz 6 has put forward the view that the lactose of 

 the mammary secretion is formed by the union of glucose, 

 the normal sugar of the organism, with galactose, which is 



1 Marshall and Kirkness, " On the Formation of Lactose," Biochem. Jour., 

 vol. ii., 1906. 



2 Puerperal glycosuria and lactosuria have been described in women in 

 a number of cases. Lactosuria is also stated to occur not infrequently in the 

 late stages of pregnancy both in women and animals, the lactose in such cases 

 being presumably derived from the mammary glands by a process of absorp- 

 tion. See Hofmeister, " Ueber Laktosurie," Zeitech.f. Phys. Chemie, vol. i., 

 1877 ; Porcher, De la Lactoaurie, 1906 ; and " L'Origine du Lactose," Arch. 

 Internal, de Phys., vol. viii., 1909. See also p. 510. 



3 Thierfelder, "Zur Physiologic der Milchbildung," Pfluger's Archiv, 

 vol. xxxii., 1883. 



4 Landwehr, "Ueber die Bedeutung des tierischen Gummis," Pftiiger's 

 Archiv, vol. xl., 1887. 



6 Foa, " Sail' Origine del Lattosio del Latte," Arch, die Fie., vol. v., 1908. 

 6 Muntz, "Sur 1'Existence des Elements du Sucre de Lait dans les 

 Plantes," Annales de Chim. et de Phya., vol. x. 



