546 Dr. F. H. A. Marshall and Mr. E. T. Hainan. 



DESCRIPTION OF PLATE. 



[The figures were drawn by the late Edwin Wilson, of Cambridge.] 



Fig. 1. — Giant cells referred to on p. 536. [This section also passed through the 

 myometrial gland, and it was intended that the cells of this gland should be shown 

 on the figure, but, unfortunately, owing to inability to supervise the drawing, as a 

 result of the outbreak of war, and the subsequent death of the artist, the figure was 

 not completed.] 



Fig 2. — Experimentally produced Placenta — Section of Uterus, showing Outgrowing 



Lobe of Mucosa, where small piece has been removed by operation. (Low power.) 

 Fig. 3. — Experimentally produced Placenta — Connective Tissue forming Decidual Cells 



which enclose Blood Capillaries. (Same section as fig. 2, more highly magnified.) 

 Fig. 4. — Experimentally produced Placenta — Part of Section of Uterus, which has been 



slit open, showing Growth of Placental Tissue in upper portion of section. (Low 



power.) 



Fig. 5. — Experimentally produced Placenta (same section as fig. 4, more highly 

 magnified) — Plexus of Blood-vessels below the Surface of the Mucosa. 



On the Post- (Estrous Changes occurring in the Generative Organs 



and Mammary Glands of the Non-Pregnant Dog. 

 By F. H. A. Marshall, Sc.D., and E. T. Halnan, M.A., 2nd Lieut., K.F.A. 



(Communicated by J. Barcroft, F.B.S. Beceived November 24, 1916.) 



[Plates 24-26.] 



The oestrous cycle in animals which come " on heat " at relatively 

 infrequent intervals {i.e. monoestrous animals) has been divided by Heape 

 into the following four periods : — 



(1) Anoestrum (period of rest). 



(2) Pro-oestrum (periods of growth and destruction). 



(3) CEstrus (period of desire). 



(4) Metoestrum (period of recuperation, occurring only in the absence of 

 pregnancy). 



This scheme of classification was adopted by Marshall and Jolly in 

 describing the changes occurring in the generative organs of the Bitch. 

 It has been shown that ovulation normally takes place during oestrus at or 

 near the termination of the sanguineous discharge which characterises the 

 pro-cestrum. This observation has since been confirmed by Keller. 

 Ovulation occurs spontaneously in bitches, the additional stimulus of coitus 

 being unnecessary. 



