Talk:Paper - Maturation of the ovum in swine (1917)

Maturation of the ovum in swine[edit] GEORGE W. CORNER

Frniii lite Aniilnmical Lnl)oratory, Universilij of California

Since the first description of maturation of the ovum of the rabl)it l>y \'an Beneden in 1875, the study of this remarkable phenonieiioii lias boon extended to certain other niannnals. with the result that practically all observers now agi'ee that two polar bodies are formed by every o\'um, the first of which is extruded from the egg while still in the ovary, but immeiliately before rupture of the follicle. Formation of the second jwlar body then proceeds to the formation of a division-spindle, but goes no farther until the egg is discharged and fertilized. .Vfter the entrance of the spermatozoon the .seconil polar body is completed and extrudcil. In the event that fertilization does not occur, the ovum degenerates in the state in which it was freed from the ovary.

Full and comprehensi\-c observations of the proc(>ss of maturation have been made in the rat (Sobotta and Hunkhard '10), guinea-pig (Rubaschkin '()o), opos,sum (Hartman 'IG), a bat, Vesperugo noctula (\'an der Stricht '08), the domestic cat (Longley '11), and the mouse. The studies of Sobotta ('95) and others, lead them to believe that in the last named species many eggs form but one polar body. The interest excited by this statement has caused the mouse to be more fully investigated than any other, with tlie result that the views ciuoted have been proven ineoiTeet. The reader is referred to the work of I>ong and Mark Cll) for details of the question together with the most comprehensive account of maturation yet presenteti in any nuimmal.

The final disproof of this supposed exceptional case raises the (|uestion as to whether the process may not be identical in all manunals. To answer this a wider .search will be necessary, for the species named above comprise but three rodents, one marsupial, one carnivore, and one chiropter. There are also old or undetailed accounts or ])reliniinary notes ujion the ova of the dog (O. \ an der Stricht 'OS), tlie rabbit (Van Beneden 75, Heape '05), the niarsuiual Dasyurus viverrinus or Australian "native eat" (Hill '10). an insectivore. Tupaia javanica (Hubrecht '95), and of a lemuroid ape. Tarsius spectrum (Hubrecht '02), and thus of the twelve orders of mammals there are four in which the process of maturation is well known in one species or more, two in which it is very obscure, anil six in which ripening ova have never been seen.

Amonp the la.«t are the ungulates, in which the species are either rare and inacces.*<ible, or if conunon, are so large that the search for the ova is very difficult. For these reasons it will be of interest to describe a small series consisting of 15 ova from 7 sows (sus scropha domesticus). I am indebted to Mr. Ralston B. Brown, Sui)eriiiten(lent of the Oakland Meat and Packing Company of Oakland. California, for the opportunity to collect the material, and to Mr. A. E. Amsbaugh and Mr. Felix H. Hurni for a.ssistance in its preparation. The sows were selected and the tubal ova found by the method given in a previous paper (Corner and Amsbaugh '17). Ovarian ova wer6 studied in serial sections of the follicles (celloidin) or by cutting hardened follicles into sliees, locating the discus proligerus and sectioning it in paraffin.

1. Killed during oestrus, probably on the first day. Unruptured follicles. Three ovarian ova sectioned, two show germinative ve.sicles, the other shows the first polar body and the second polar spindle.

2. First or second day of oestrus. One follicle ruptured, its ovum not found in the tubes. An ovarian ovum shows the first polar body and the second spindle.

3. Second or third day of oestrus. All follicles ruptured. Four imfertilized tubal ova sectioned: all show the first polar body and the second .sj)indle.

4. History unknown. Five unfertilized tubal ova found, of which four (studied fresh) show one polar body extruded.

5. Probably socoml day of oostrus. Copulation obsen'ed 24 hours before killing. One tubal ovum found, covered with spermatozoa. In sections, the male and female pronuclei are in contact. Two polar bodies.

0. Second or third day of oostrus. Copulation observed 10 hours before killing. Two ova found in the tubes; both were covered by spermatozoa. One of them, studied fresh, showed two polar bodies. The other was sectioned, and showed the pronuclei in contact, but unfortunately the polar bodies were obscured by damage to the sections.

7. Tubes contained segmenting ova of 2, 4. and G blastomeres. One of the two-celled embryos (studied fresh) showed two polar bodies; a favorable view of the others could not be obtained.

COXCLUSIOXS

The first ova of an ungulate mammal to be studied indicate that the sequence of maturation is the same in swine as in previously stuilictl forms of other orders, the first polar body being extrudetl and the second polar division proceeding as far as spindle formation before fertilization, the second polar body being cut off only after the entrance of the spermatozoon.

LITERATURE CITED

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