that they either were sterile or they contained dead 

 embryos. From one of these eggs Wolff extracted a monster 

 chicken, which provided the subject of the following descrip- 

 tion (Tig s « 11 - 12). The chicken looked completely ready 

 for hatching. It had a single head, neck, thorax and abdomen, 

 but the extremities were four pairs in number: two pairs of 

 legs and wings. The situation of the extremities was such 

 that it was easy to distinguish the natural from the additional 

 The additional legs were attached to the thighs at the sacral 

 region and directed to the head end of the chicken, i.e. in 

 a situation opposite the natural legs. The origins of the 

 additional wings were located backwards from the origin of 

 the additional legs in the coccyx region. The impression is 

 that the additional wings and legs belong to another 

 undeveloped chicken, which is located on the original 

 chicken. The underdeveloped chicken is positioned as if 

 the head and neck of the first are hidden in the pubic 

 region of the formed partner, and the chest and abdomen 

 are embedded in the sacral region of the latter, so that 

 externally only the legs and wings appear. 



On opening it, Wolff found that the abdominal protuberance 

 contained a single yolk. In the structure of the internal 

 organs of the primary chicken, no deviations from normal were 

 seen with the exception that instead of the two blind out- 

 growths of the intestine there were three. All of the internal 

 organs related to the primary chicken, and in the second 

 there was nothing except the extremities — neither neck, nor 

 head, nor abdomen, nor thorax nor an internal cavity. 



The article is terminated by a quick comparison with the 

 monsters described in literature and does not contain any 

 general conclusions. This is entirely natural, because earlier 

 Wolff had published another teratological work about the 

 double-headed calf, which was accompanied with a theoretical 

 chapter containing conclusions related to the above-described 

 monstrosity. The material described in the last mentioned work 

 is a calf which died at birth. It had two heads and two necks, 

 but a single chest, abdomen and a normal number of extremities. 



3. Wolff, "Descriptio vituli bicipitis cui accedit 



commentatio de ortu monstrorum," NOVI COMMENT. ACAD. 

 SCI. PETROP., XVII, 1773, pp. 540 - 573. 



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