80 THE PHYSIOLOGY OF REPRODUCTION 



changes of monkeys. The cycle is divided into four stages, 

 as follows : 



(1) The Constructive Stage. 



(2) The Destructive Stage. 



(3) The Stage of Repair. 



(4) The Stage of Quiescence. 



The last stage may conveniently be considered first. 



The Stage of Quiescence. The normal condition of the human 

 endometrium has been described by Webster, 1 to whose account 

 the reader is referred. This author calls special attention to 

 the following points : (1) The thickness of the mucosa is not 

 uniform, but varies considerably. (2) The epithelial cells which 

 line the mucosa, and also those which line the glands, show 

 differences in shape and size, and in the position of the nuclei. 

 (3) The epithelial cells lining the glands are, as a rule, larger 

 than the superficial cells. (4) The interglandular connective 

 tissue or stroma is mainly embryonic in nature, and consists of 

 a nucleated protoplasmic reticulum, containing every stage of 

 transformation into the more differentiated spindle-shaped cells. 

 (5) The stroma nearest the surface is for the most part arranged 

 parallel to it, the cells immediately below the epithelium 

 forming a kind of basement-membrane. (6) The superficial 

 portion of the mucosa is supplied only by capillaries. (7) The 

 line of junction of mucosa and muscle- wall is irregular, and 

 there is no special muscularis mucosse. 



The Constructive Stage. During this stage the stroma of the 

 uterus undergoes a process of growth. This is brought about 

 partly by cell division, partly (according to Engelmann 2 ) by 

 an increase in intercellular substance, and partly by an enlarge- 

 ment of the glands and blood-vessels. According to Lipes, 3 

 this stage commences as soon as the process of regeneration 

 (following the preceding menstrual period) is completed, which 

 is about eighteen days after the cessation of the previous 

 flow. " During the stage of regeneration the cells of the stroma 



1 Webster, Human Placentalion, Chicago, 1901. 



2 Engelmann, The Mucous Membrane of the Uterus," &c., Amer. Jour. 

 Obstet., vol. viii., 1875. 



3 Lipes, " A Study of the Changes occurring in the Endometrium during 

 the Menstrual Cycle," Albany Medical Annals, vol. xxv. 1904. 



