Animal breeding / by Laurence M. Winters.

  • Winter, Laurence Merriam, 1891-
Date:
1925
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Animal breeding / by Laurence M. Winters. Source: Wellcome Collection.

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    50 TWINS before the 11 mm. stage. When the vesicles are about 15 mm. long, the two chorions are overlapping and ready for fusion. From this time on, fusion of the chorions and vas¬ cular anastomosis begins to take place; and there is a free exchange of blood between the two after the 15 mm. stage (Fig. 10). WTien the 75-80 mm. stage is reached, fusion of the chorions is perfect. Fig. 10.—Twin chorionic vesicle of cow. (After Lillie, courtesy The Journal of Experimental Zoology.) 1, Arterial through trunk; 2, cotyledon with venous connection with both sides; 3, amniotic sacs opened; 4, clitoris of free-martin. 54. The Hormone Theory.—The above facts give rise to Lillie's hormone theory of the free-martin which, in brief, is that the male calf casts hormones in its blood, these flow to the female calf and stimulate the recessive characters present in the female embryo, thus causing the sterile free- martin. In all the cases of two-sexed tAvins, examined by Lillie, where vascular anastomosis had taken place, the female was a free-martin; and where vascular anastomosis had not taken place, the female was sexually normal. He also found cases of male twins, and also female twins, луЬеге