234 



NOTES AND MEMORANDA. 



preparation for the reception of the ovum. It is much more impro- 

 bable that the uterus during the menstrual flow is in a condition 

 suitable for this function — mth a retrogressive process going on in 

 the mucosa, its vessels ruptured, and its surface discharging blood. 

 It is even more improbable that the mucosa in this state of degenera- 

 tion will on the descent of an ovum take on a totally opposite process, 

 and become highly developed. The type of the impregnated uterus is 

 seen in the active uterus when the mucosa is swollen and menstrua- 

 tion has not yet commenced. If the bleeding does commence, it is a 

 sign that the ovum has perished, and that the mucosa is returning to 

 its state of rest. Thus we arrive at the highly important conclucion 

 that a developing ovum, or growing embryo, belongs not to a men- 

 strual period just past, but to one just prevented by fecundation. 

 Lowenhorst has already expressed this opinion from a consideration 

 of the clinical aspects of menstruation, and we believe that the method 

 of calculating the duration of pregnancy suggested by the new facts 

 is not altogether a new one among the gynaecologists and practitioners 

 of this coimtry. 



NOTES AND MEMOKANDA. 



Browning's New Microscope. — This instrument, which was ex- 

 hibited by Mr. Browning, F.R.A.S., at the last suiree of the Eoyal 



Society, and which is illustrated in 

 the adjacent cut, promises to afford 

 many advantages to the scientific 

 worker. It is really the adaptation 

 of a well-known foreign plan, to 

 the English microscope. Various 

 schemes have been adopted for the 

 purpose of getting a satisfactory 

 rotating stage, but save in very ex- 

 pensive instruments they have failed 

 through imperfection in the work- 

 manship, so that, the centering not 

 being perfect, objects sometimes 

 almost travelled out of the field of 

 view. With the contrivance adopted 

 in the present instrument this ab- 

 sence of centering is impossible, for 

 by a special adaptation, both body 

 and stage being one piece, they re- 

 volve together. Hence, of course, the 

 object is as central in one position 

 as another. There are, to be sui'e, 

 , some slight disadvantages, as, for 

 i instance, the interference of the body 

 ^ at one point of the circle, and the 

 disadvantage of a monocular as com- 



