THE ALBUMIN LIGAMENT (Ligamentum albuminis) is 

 the structure located, so Tredern thought, on the border 

 between the external fluid and the internal thick egg albumin. 

 These two layers of egg albumin Tredern called the primary 

 and secondary egg albumin respectively CAlbumen primum and 

 Albumen secundum) . In detail he described the different parts 

 of this ligament and its relation to water and acid; in 

 short, he did not doubt its constant existence. Later, 

 however, Baer showed that the structure did not represent 

 an independent membrane or ligament, but only the surface 

 layer of the second (middle) layer of the albumin which was 

 connected with the first (external) layer at the pointed end 

 of the egg. This membrane, according to Baer,! 1 appeared only 

 in an egg opened in water. Upon removal of the membrane formed 

 in water, it developed again. Baer agreed with Purkinje, 

 who considered the reproduction of the membrane as evidence 

 that it was not a constant structure but only a result of 

 water acting upon the surface of the thick albumin. 



DEVELOPMENT OF THE JAWS AND BEAK. Some earlier 

 authors had noted the presence of the beak at about the 

 fifth day of incubation (Haller, Wolff, Malpighi) (53) and 

 some had related its appearance to different periods of 

 embryonic life (Koiter, Vesling, Stenon, Lengli, and Shrader) 

 (54) . Tredern concluded that on the fifth day (rarely, on 

 the fourth day) it was possible to see the first beginnings 

 of the beak. Occasionally the lower jaws appeared earlier than 

 the fourth day, when along the sides of the neck two branches 

 appeared. The upper jaw is usually seen somewhat earlier than 

 the lower, but its halves remain disconnected longer. The 

 central growths of the upper jaws from the forehead have at 

 first the shape of a cluster (Figure 18, 36, 46). They are 

 separated from smaller blunt growths by two slits (Figure 18, 

 4), which later are converted into the nostrils. These blunt 

 growths later Cat the fifth day) join with the side parts of 

 the upper jaw CFigure 18, 36, 45). The forehead cluster 

 gradually forms the back of the upper jaw (55) (Figure 18, 

 44, 51). On the seventh or eighth day the beak starts to be 

 covered with a cartilaginous case, which is almost always 

 more constructed in the upper jaw than in the lower (56) . 

 This cartilaginous capsule gets its beginning from one small 



11. Baer, UBER ENTWICKLUNGSGESCHICHTE , Vol. 2 (1953), 

 p. 22. 



222 



