were completely formulated) . The second case was the 

 doubling of the head end, beginning from the girdle region; 

 the monster had three correctly- formulated hands, two normal 

 and one underdeveloped legs. The description of the monsters 

 (the first case was illustrated by two excellently-engraved 

 figures, representing the twins from the front and from 

 behind) was concluded with a brief account about the reason 

 for the monsters appearance. By comparison of the described 

 cases, Ozeretskovskii made the conclusion that monsters 

 can be very variable and that each monster, must possess 

 its natural cause. "The physiologists — Ozeretskovskii 

 wrote — must explain these causes and find the specific 

 original source of these monsters — whether their origin is 

 due to the union of two embryos, or from strengthened, 

 weakened or incomplete development of parts of the body" 

 (p. 371). 



In another article, whose contents were received by the 

 Academy one year before (on October 25, 1798)1, a description 

 was given for non-hatched hen's egg with an opening in the 

 shell; through this opening the end of a blood vessel passed. 

 When the egg was opened, in addition to yolk and egg white, 

 a pear-shaped body was found in it, which was full of clotted 

 blood. Ozeretskovskii considered the described content in 

 the egg as a polyp of the oviduct, torn at the time of yolk 

 passing, falling in the egg together with the white. In 

 connection with this, he assumed, that the presence of similar 

 kinds of strange bodies in the eggs of birds may be the cause 

 of appearance of monsters, as the mechanical pressure on the 

 delicate parts of the developed embryo inevitably leads to 

 their deformation. During this, Ozeretskovskii referred to 

 cases of development in double-yolk eggs of doubled embryos 

 which — as a rule — are monsters. During more or less normal 

 development of these twins, they can unite with each other. 

 "Some years before" Ozeretskovskii wrote "we saw here, in 

 Petersburg, doubled chickens, hatched from one egg, provided 

 with all organs and united at the backs; when one of them 

 stood on the legs, the other lied on it on the back with legs 

 upwards in the most unnatural position. It is clear that, 



1. N. Ozeretskovskii. De ovo perforata. There also, 

 12.1801, pp. 364-368. 



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