78 Translation from Purkinje 



§ 15 



Concerning the so-called third albumen and 



the zone of the chalazae. 



In investigating the question of a third albumen, beware lest you 

 delude yourself as others* have done and as I, too, did for a long time. 

 It is true, of course, that the albumen about the central whitish strand 

 of the chalaza is thicker and almost approaches gelatin, and if you 

 wish to call it the third albumen to distinguish it more precisely, I 

 have no objection, although it does go over gradually at the extremi- 

 ties of the chalazae into the rest of the albumen so that it cannot be 

 [[19] delimited in any way. The mound, however, which the cited author 

 figures about the chalaza and which is continued in the form of a 

 girdle to the other end of the egg, where it surrounds the chalaza, and 

 also what he calls the "ambient chalaza" and the "third albumen," 

 all this is not real, but an oblique view of the outer surface of the 

 second albumen, closely applied to the yolk and chalazae after the 

 rest of the albumen has settled to the bottom of the dish by its own 

 weight and diffused. In my opinion, at least, it seems to present an 

 optical illusion because of a peculiar surface. Those who used to talk 

 about a normal girdle of the chalaza surrounding the cicatricula and 

 embracing the yolk sphere [dividing it] at a ratio of 80:100 seem to 

 have suffered from a similar illusion. 



§16 



A membrana propria of the albumen is denied. 



Writers are also wont to talk about a membrana propria of the 

 albumen, but I greatly doubt whether anyone has seen it unless he 

 has first produced it artificially, since fresh water forms it by coagu- 

 lation wherever the water has touched the albumen. I have succeeded 

 best in making a membrane of this sort apparent by the following 

 procedure: You keep a fresh egg after removal of the shell immersed 

 in cold water for several hours. The albumen then develops a rather 

 solid whitish surface. You may now suck off the water surrounding 

 the albumen and insert a slender tube into it as far as the root of the 

 chalaza and inflate the albumen by blowing gently. It gradually swells 

 up into a bubble almost 6 times the volume of the egg. If the operation 

 goes off well, it retains its shape and remains intact. You may then 

 again gently pour on water so that the ovum, now floating freely, may 

 be expanded on the under side where the bottom of the dish pre- 



' * Comes ab Tredern [Louis Sebastien Marie de Lczerec de Tredern]: Diss[ertatio 



Inauguralis Medica] sistens Ovi Avium Historiae \et Incubationis] Prodr\omium. 

 (Jenae: 1808)], Figs. 2 and 3. [German translation by L. Stieda, Wiesbaden: 1901.] 



