46 Miss J. E. Lane-Claypon. On the Origin, etc., of [June 16, 



follicles which have almost reached full maturity, and it is a well-known 

 fact that rabbits can be readily fertilised immediately after parturition. 



The gland, although soft, is not in any way brittle, and in spite of its 

 great general enlargement retains on the whole the same shape, the most 

 marked change being that from the wedge-shaped to the circular transverse 

 section. 



Changes in Size of the Interstitial Cells. — This great increase in size must 

 be the result either of a large numerical increase, or of a very great increase 

 in the size of the individual ovarian cells. The latter is at any rate the 

 main, if not the only factor concerned, the change in size of the cell under 

 the microscope being so marked as to attract attention even apart from any 

 actual measurement. 



The measurements were made with a micrometer eye-piece, gauged against 

 a micrometer slide, this method being found quite sufficiently accurate for 

 the purpose. It was not intended to record exactly the size of each 

 individual cell, but rather by taking the measurements as accurately as 

 possible of a large number, to find the average increase in size at different 

 stages of pregnancy. In taking the measurements considerable selection was 

 exercised in the cells measured ; only those whose area in section was 

 approximately circular, and where the nucleus was centrally situated being 

 used, as it was hoped by these precautions to obtain measurements passing as 

 nearly as possible through the centre of the cell. The measurements are 

 given below of 10 cells from each date of pregnancy, but this does not by 

 any means represent the number actually measured, but the same figures 

 recur again and again, and the average works out to almost precisely that 

 given. 



Towards the end of pregnancy there is considerable difficulty in finding 

 the right kind of cells to measure, nearly all of them being angular and 

 irregular in outline, giving as a whole somewhat the appearance of a 

 tesselated surface. The changes in general aspect of the sections, produced 

 by the change in the size of the cells, will be returned to later on. 



