1905.] the Interstitial Cells of the Ovary in the Rabbit. 38 



day, the transformations which have been taking place in the deutobroque 

 cells must be briefly touched upon, but they have been so fully described by 

 v. Winiwarter that a lengthy exposition is quite unnecessary. I shall adopt 

 his nomenclature throughout. It has already been stated . that almost 

 immediately after birth changes begin to take place in the deutobroque cells, 

 which enter upon the leptotenic phase, the transformations beginning centrally. 

 This is succeeded by the synaptenic, and by the third day there are already 

 a very great number of this variety. 



The leptotenic phase is characterised by the absence of visible nucleolus, 

 and by the spreading out of the chrcmatin in the form of fine filaments over 

 the whole nuclear area. This stage is evidently only a further step in the 

 differentiation which has already taken place. It has been shown that the 

 change from the protobroque to the deutobroque type is accomplished by the 

 chromatin masses becoming gradually broken up into strands. In the 

 leptotenic phase the process is merely carried further. Whereas in the 

 deutobroque stage there are still one or two chromatin masses which have not 

 become broken up into strands, in the leptotenic this is not the case, the whole 

 chromatin being present in the form of filaments. The transition stage can 

 be seen in an ovary of a few days after birth (fig. 6 (1)). These filaments 

 become gradually aggregated, passing to the synaptenic state. The leptotenic 

 condition is a very fugitive one, whereas the synaptenic, owing presumably to 

 the great variety of aspects through which the aggregation passes is very 

 much more prolonged. The synaptenic is succeeded by the pachytenic, where 

 the filaments are coarser, then by the diplotenic, and this in its turn by the 

 dictyate condition, which is the typical nuclear appearance of the young ovum. 



These changes pass gradually outwards, and by the tenth day even the cells 

 quite at the periphery have passed through the earliest phases, whilst the 

 central cells are reaching the final ones. By the fourteenth day there are a 

 certain number of dictyate nuclei towards the centre. At this stage the 

 central mesoblastic core is becoming obliterated, the egg-clusters of either 

 side of the ovary very nearly meeting. The clusters are much smaller, 

 having been split up by the ingrowing mesoblast. The number of dictyate 

 nuclei now increases at a surprising rate, there being a great number by the 

 fifteenth day, and a still greater number by the sixteenth day, by which time 

 the clusters are almost indistinguishable, except round the periphery, their 

 place having been taken by dictyate cells, some of which now show a 

 surrounding follicular epithelium. There are also collections of small more or 

 less rounded cells lying in between the young follicles, but not forming any 

 part of the follicular epithelium. These are the interstitial cells of the ovary, 

 and I propose now to trace their origin in detail. 



