THE CESTROUS CYCLE IN THE MAMMALIA 63 



regarding the- behaviour of the metabolism. Schroder,i who investi- 

 gated the nitrogen metabolism, found a retention of nitrogen 

 immediately before Eind during menstruation (c/. Potthast, etc., for 

 dogs, p. 49), but other investigators have obtained somewhat different 

 results.^ Zuntz has shown from numerous experiments that, contrary 

 to the conclusions of other authors, there is no evidence of a 

 constant variation in the respiratory exchange during the menstrual 

 cycle. (For changes during pregnancy, seeT)hapter XI.) 



Mosher ^ states that there is a fall of blood pressure at the time 

 of menstruation. Zuntz ^ records a diminution in the pulse-rate. 



Sfameni^ states that there is a decrease in the quantity of 

 htemoglobin in the blood during menstruation. He says also that 

 the number of blood corpuscles increases in the days immediately 

 preceding the haemorrhage, but is diminished during it.® 



Birnbaum and Osten^ state that in the blood of menstruating 

 women coagulation is retarded. This statement is based on 

 experiments made by adding fibrinogen to menstrual blood-serum. 



Blair Bell ^ states that in connection with menstruation there is 

 a marked drop in the calcium content of the systemic blood, and 

 that this is most marked just before bleeding begins. This is 

 correlated with an excretion of calcium salts in the menstrual 

 discharge, an examination of which revealed the presence of a 

 considerable quantity of calcium, both free and within the leucocytes 

 (see p. 81). This excretion of calcium during menstruation is 

 regarded by Blair Bell as connected phylogenetically with the 

 process of egg-formation by birds and other lower Vertebrates. 



Further, this author is disposed to believe that the calcium 

 metabolism, under the direction of the ovaries and other ductless 

 glands, is concerned in the phenomena of menstruation. He refers 

 especially to the following points: (1). Calcium salts are necessary ' 

 for the repair of all lesions. Therefore the presence of menstruation 

 is dependent upon a healthy condition of the organism, and its 

 claims on the calcium metabolism at any particular time {cf. absence 



1 Schroder, " Untersuchungen iiber den Stoffwechsel wahrend der Men- 

 struation," ZeiUchr. f. hlin. Medicin, vol. xxv., 1894. 



2 See von Noorden, loc. cit. 



' Mosher, "Blood-pressure during Menstruation,'' Johns Hopkins Hospital 

 Bulletin, 1901. 



* Zuntz, loc. cit. 



^ Sfameni, loc. (At. 



° Cf. Carnot and Deflandre, " Variations du nombre des H6niaties chez la 

 Femme pendant la p6riode menstruelle," C. R. de la Soc. de Biol., vol. Ixvi., 

 1909. 



' Birnbaum and Osten, "Untersuchungen iiber die Gerinnuiig des Blutes 

 wahrend der Menstruation," Arch. f. Gynilk., vol. Ixxx., 1906. 



" Blair Bell, " Menstruation and its Relation to the Calcium Metabolism," 

 Proc. Roy. Soc. Med., July 1908. See also below, p. 389. 



