420 



SCIENCE 



[N. S. Vol. LIU. No. 1374 



microscope as light spots -without the iodine 

 treatment, and an enormous number of the 

 cells are scattered over the yolk sac. The 

 cells of the small-mouthed black bass are 

 large and contain much glycogen which dis- 

 solves very readily in water after iodine stain- 

 ing. I have noted in pike-perch which have 

 been kept under observation for a consider- 

 able time that their glycogen cells become 

 greatly diminished ia number. I have not 

 been successful in finding the glycogen cells 

 in all species of fish. I have never been able 

 to discover them in Fundulus, and have sought 

 for them in vaia in recently hatched smelt 

 They evidently act as temporary reservoirs of 

 glycogen, but why they are present in some 

 species of recently hatched fish, and not in 

 others, is not apparent. 



If it should be discovered that these 

 peculiar cells can be isolated and satisfac- 

 torily cultivated in artificial media, they will 

 offer most promising material for studying 

 experimentally the formation of glycogen. 



Frederick W. Ellis 



MoNsoN, Mass., 

 August 23, 1920 



THE OVARIAN CYCLE OF SWINE 



Most of our information regarding the 

 changes in the mammalian ovary during the 

 various events of the reproductive cycle has 

 been gained from study of the laboratory 

 rodents and small carnivores. The domestic 

 ungulates, on account of their large size 

 and commercial value, have been neglected 

 in this respect, although they promise certain 

 advantages because of the simplicity of their 

 ovarian structure and the regular, outspoken 

 appearance of oestrus. 



The only attempt to follow the history of 

 the ripening follicles and the corpora lutea 

 of an ungulate, with material of known his- 

 tory, is that recently published by Max 

 Kiipfer of Zurich,^ who made use of the 



1 Kiipfer, Max, ' ' Beitriige zur Morphologie der 

 weibKchen GeseHecitsorgaoae bed den ^augetieren, ' ' 

 Benksschr. d. Schweis. Naturf. Gesellsch., 1920, Bd. 

 LVI. 



municipal abattoir of that city to procure a 

 large series of ovaries of the cow. He was 

 able to obtain records of the last appearance 

 of oestrus in a certain number of animals 

 (apparently 33) and has given a set of hand- 

 some plates illustrating the rise and retro- 

 gression of the corpus luteum. From the 

 gross appearances and from measurements (no 

 microscopic studies were made) Kiipfer states 

 that the interoestral period of 21 days may be 

 divided into two parts. During the first 

 10-11 days after ovulation the corpus luteum 

 is slowly reaching its full size, and thereafter 

 it is in a state of retrogression which con- 

 tinues throughout the next interval, until by 

 the time of the second following ovulation (42 

 days) the corpus luteum is macroscopically 

 insignificant. The ovaries of animals under- 

 going uninterrupted oestrus cycles will there 

 fore contain the follicles and corpora lutea 

 of two or three periods, at successive stages 

 of growth and retrogression. 



The present writer has been endeavoring to 

 piece out a similar account of the pig, in 

 order to provide an anatomical basis for the 

 physiological relations of ovary, ovum, and 

 uterus in this species, and has published^ a 

 description of the mature follicles and devel- 

 oping corpora lutea up to the tenth or 

 eleventh day, but has been unable, until the 

 present, on account of conditions of the meat- 

 packing trade, to follow the animals longer 

 than this time. The lacking material has 

 now been supplied, through tlie cooperation 

 of Mr. W. N. Cooper, manager of the Amer- 

 ican Feeding Company of Baltimore, at whose 

 large piggery farm a series of 22 sows has 

 been obtained covering practically every day 

 of the 21-day cycle. 



The story as read from these specimens is 

 a simple one, as will be seen from the accom- 

 panying diagram. It appears that mature 

 ovaries of non-pregnant animals contain a re- 

 serve stock of follicles of 5 mm. diameter or 



2 Corner, G. W., ' ' On tie origin of the corpus 

 luteum of the sow from both granulosa and theea 

 interna," Amer. Jour. Anat., 1920, Vol. 26, pp. 

 117-183. 



