SECT. 6] OF THE EMBRYO 859 



Since the time of Aggazzotti several workers have occupied them- 

 selves with the same problems. Healy & Peter examined the yolk 

 and white during the early part of development with the special 

 intention of finding what buffers were there. They obtained figures 

 of j&H 6-2 to 6-6 for the yolk and 8-2 to 8-4 for the white, and they 

 confirmed the observation of Aggazzotti that no change took place 

 over a long period if the eggs were not incubated. They estimated 

 the alkali reserve of the white by titrating to different end points 

 with jV/io HCl. Thus the following figures, 



White 



Yolk 



Phenolphthalein Methyl orange Phenolphthalein 

 c.c. jV/ioHCl c.c. jV/ioHCl c.c. ^'/lo NaOH 



Incubation of 3 days 1-4 15-3 5-2 



,, 6 days 1-7 14-8 12-9 



indicated that the main part of the alkali reserve was in the form 

 of sodium and potassium carbonate. Parlov confirmed Aggazzotti's 

 results on the egg white, using the ingenious method of boring a 

 hole in the shell and withdrawing samples each day of incubation. 

 The/>H fell from g-o to 7-0. A good deal of evidence exists that the 

 high alkalinity of the egg-white of the new-laid egg is due to the escape 

 of COgfrom it (see Fig. 152)^. Thus Buckner & Martin found oviducal 

 egg-white to be at p¥L 6-7 though after laying the usual figure of 9-0 

 was obtainable, and similar results were reported by Romanov & 

 Romanov in a complete research which gave curves resembling 

 closely those in Fig. 211. The alkalinity of the new-laid egg-white is 

 connected with its bactericidal properties for a discussion of which 

 see Section 19-3. 



Vladimirov also measured electrically the pH of the white of 

 the hen's egg during its development. His figures are shown in 

 Fig, 211 plotted on the same graph as those of Aggazzotti. It is 

 interesting that the fall in pH takes place at exactly the same 

 rate as found by Aggazzotti, but always about one pH unit 

 higher than those of the Italian worker. The still more recent figures 

 of Buytendijk & Woerdemann agree with those of Vladimirov 

 rather than with those of Aggazzotti, a fact which is all the more 



1 In an atmosphere containing 1 2 % COj the pH of the egg-white remains constant 

 at 7-8 for the first six days after laying, showing neither the usual rapid rise nor the 

 usual slow fall (Fig. 211). And the pH may be varied at will by adjusting the external 

 carbon dioxide concentration (Romanov & Romanov). 



