THE CORPUS LUTEUM OF THE GUINEA PIG 



I. W. Rowlands 



Agricultural Research Council 

 Institute of Animal Physiology, Babraham, Cambridge 



The salient morphological and histological features of the 

 ovarian changes in the guinea pig have been known for half a 

 century. In 1906, Loeb described its early development and 

 drew attention to the early closure of the rupture point of the 

 follicle, the formation of a fluid-filled central cavity and to the 

 occurrence of haemorrhage before the obliteration of the cavity 

 by luteal tissue. In a later paper, Loeb (1911) gave a compre- 

 hensive account of the histology of the ovary during the di- 

 oestrous cycle and pregnancy, taking into account the corpus 

 luteum and follicular activity. He noted the greater size of 

 the former during pregnancy and that it remained a large 

 circumscribed organ until parturition. Nevertheless, cy to- 

 logical evidence of regression was obtained which seemed to 

 be associated with loss of vascularity. A rapid and complete 

 degeneration of all vesicular follicles was noted in unmated and 

 pregnant animals for a short period of about four or five days 

 after ovulation, after which follicular growth was resumed, 

 and by the 10th day large healthy follicles together with 

 others showing signs of recent degeneration accompanied the 

 corpora lutea. A number of the healthy follicles soon undergo 

 very decisive changes which are best described in Loeb's own 

 words — "These follicles are characterized by an increase in 

 cytoplasm of the granulosa cells. The nuclei of the granulosa 

 cells are not so densely packed in these follicles as in the ordi- 

 nary large follicles; this peculiarity being due to the marked 

 development of the cytoplasm. They can easily be recognized 

 in sections stained by haematoxylin and eosin insomuch as 

 they appear stained more reddish in contradistinction to the 

 ordinary large follicles in which the blue colour of the nuclei 

 predominates, while in the mature follicles the red stain of the 

 cytoplasm is a distinguishing feature". 



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