Geome W Bartelmez 



° / / 



and chalaziferous] apart under water, using two paiis of forceps. 

 There are eggs in which it is obvious to the naked eye that the chalazif- 

 erous membrane is loosely attached to the vitelline [membrane] only 

 at the insertion of the chalazac (fig. 23). There are others in which 

 the central strand does not end at the vitelline membrane but at an 

 interpolated globule of albuminous substance covered by the chalazif- 

 erous membrane.'-* 



§ 14 



Of the whitish zone on the 

 surface of the yolk. 



In a great many eggs (fig. 24) one or several white strands extend 

 from one or the other central chalazal strand through the chalazif- 

 erous membrane on the surface of the yolk, running in no regular 

 w^ay, now on one side, now on the other, or encircling the whole yolk, 

 as if the membrane had been thickened or folded there. These con- 

 [ 18 ^ stitute what Vicq d'Azyr* calls the zona albicans; they are very differ- 

 ently disposed in different eggs and do not, as some claim, have a 

 constant form and relation to the yolk. They are nothing but unmis- 

 takable remains of the chalaziferous membrane. These strands usually 

 run out from the smaller chalaza at the blunter pole, which being 

 sometimes twisted obliquely passes over into them. There are fre- 

 quently many of them running over a part or the whole of the surface 

 of the yolk, avoiding in general the cicatricula; but sometimes they 

 pass over the middle of it. If you tease off the chalaziferous membrane, 

 it is sometimes possible to demonstrate folds; but usually they are not 

 folds but thickened matter of the membrane itself, giving a silvery 

 sheen like a tendon. 



At times strands of this kind are to be found only at the blunter 

 pole of the egg and there is no sign of a chalaza. j- Then the albinnen, 

 too, is found to be much diminished at the blunter pole of the egg, 

 almost all of it being gathered at the sharper end. If you were to look 

 into the origin of this condition in the oviduct, you would say it is 

 due to a too rapid secretion of albumen, namely that the part of the 

 yolk which precedes in the passage down the oviduct stimulates its 

 membrane to a copious secretion and quickly exhausts it so that when 

 the upper end of the yolk moves into the same region little is left to 

 be secreted. These conditions in isolated accidental cases also explain 

 why, under normal conditions, there is a smaller chalaza at the 

 blunter pole of the egg as well as a lesser amount of albumen. 



* Oeuvres, Vol. 4, p. 392. [Fel. Vicq d'Azyr: Fragmem sur I'Anatomie et la Physio- 

 logie cle I'Oetif, etc. (Paris: 1805).] 

 f See Leveiile (as cited), p. 416. 



