180 PHYSIOLOGY CHAP. 



(c) After total extirpation of the uterus periodic ovulation 

 is not suspended (Abel). 



(d) Ovulation may persist even after the ovary has been 

 detached from its normal anatomical relations and transplanted 

 in another part of the abdominal cavity (Knauer, Grigorieff, 

 C. Foa, Morris). 



In contrast to this independence of the function of the ovary 

 is observed a strict subordination of the periodic function of the 

 uterine mucosa to the presence of the ovary, and to its periodic 

 functional slate : 



(a) The proliferation, congestion, and haemorrhagic process 

 of the uterine mucosa appear periodically only when the 

 ovary is functioning, that is, is capable of maturing the ovum. 

 In fact, menstruation begins with puberty, when the process of 

 maturation of the ova is initiated, and ceases at the critical epoch 

 (at 45 to 50 years), when the ovary undergoes physiological in- 

 volution. 



(ft) After complete spaying the menstrual flow ceases entirely. 

 There are not wanting rare exceptions to this rule (Romiti and 

 others), but it is doubtful whether the case can be considered as 

 one of true menstrual flow, rather than irregular and pathological 

 metrorrhagia (Gusserow). 



(y) Strassmann (1870) carried out a series of experiments on 

 animals, with the object of producing by means of injections an 

 artificial increase of pressure in the parenchyma of the ovary, 

 on which depends the increase of volume of the follicle in the 

 course of maturation. The animal so treated showed in its 

 behaviour, and in the uterine mucosa, the same signs which are 

 observed during ovulation. 



These facts demonstrate that the periodic increase in size of 

 the follicles is one of the direct causes of the periodic function 

 of the uterine mucosa. 



The periodic variations of functional tone of the entire organism 

 are also an effect of the periodicity of ovulation. They are not, 

 in fact, any longer noticeable after spaying, and after the critical 

 period or menopause. As to the undeniable connection, now 

 admitted by all, between ovulation and menstruation, there exist 

 two principal theories one formulated by Pfliiger (1865) and 

 the other by Lowenhart, Keichert, Gusserow (1874), His (1880), 

 and Sellheim (1907). It is unnecessary to take into account 

 more ancient theories which to-day can only have a simple 

 historical interest. Pfliiger considered menstruation as a freshen- 

 ing, in a surgical sense, of the uterine mucosa, necessary in order 

 that the fertilised ovum which arrives there from the oviduct 

 may become adherent, graft itself there and develop, in the same 

 way that it is necessary in plants and in animals to incise or 

 freshen the parts to which it is wished to join the graft. To - 



