1905.] the Interstitial Cells of the Ovary in the Rabbit. 40 



This passage inwards of cells from the periphery was noticed by Buhler ; 

 he realised that the number of small cells near the centre during the height of 

 ovogenesis was not enough to provide a follicular covering for all the young 

 ova which were there, and he describes the streaming inwards of the cells 

 from the periphery, and their passage to the young ova, around which they 

 arranged themselves, and formed the follicular epithelium. 



Balfour noticed that in the later periods of ovogenesis there were present 

 too many of the small cells, like the follicle cells, for them all to become 

 arranged around the ova and give rise to the follicular epithelium. He was 

 at a loss to account for the destiny of these supernumerary cells, and supposed 

 that they must either eventually become ova or follicle cells, or be used up as 

 food-stuffs for the other cells. 



It seems to me, however, that these cells, supernumerary as far as the 

 follicular epithelium is concerned, are in reality very important. They form 

 the groups which represent the interstitial tissue of the fully-formed ovary, 

 and thus, far from being unimportant, are absolutely essential for the 

 performance of the functions of the ovary. 



The question which now arises is, where do these cells come from, and 

 what is their history of formation ? It has already been indicated that the 

 number of unchanged deutobroque cells varies inversely with the number of 

 these cells, since these last are greater in number in the region where there 

 are most deutobroque cells present, namely, at the periphery, especially in the 

 region of the poles, and the high power of the microscope reveals the fact that 

 these cells are indeed metamorphosed deutobroque cells. 



The ordinary deutobroque cell presents one or two irregular chromatin 

 masses, from which pass out filaments of varying degrees of coarseness and 

 fineness with nodules at their intersections. The centre of the nucleus 

 is clear, whilst around the periphery is the granular appearance already 

 described. See fig. 2 (/). In the ovary of about the eighteenth day the only 

 regions where these cells are to be seen in any appreciable numbers are 

 round the periphery and at the poles. They stand out even under the low 

 power on account of their general transparent aspect as compared with the 

 surrounding cells, and also in many cases on account of their rather larger size. 

 There are also cells whose transparency is not so great, but which show up 

 quite markedly in contrast to the rest and are rather smaller in size than the 

 more transparent ones. These cells are transformation stages between the 

 deutobroque and the ordinary interstitial type, and the process resembles very 

 much in the inverse order that which has been already described for the 

 deutobroque formation from the protobroque. 



The first stage is the gradual massing of the chromatin into irregular masses 



